EXTRA DIVISION, INNER HOUSE, COURT OF SESSION
 CSIH 24
OPINION OF THE COURT
delivered by LORD BRODIE
in the Reclaiming Motion
SHELLEY ELIZABETH ROMEIN
Petitioner and Reclaimer;
THE ADVOCATE GENERAL FOR SCOTLAND
ON BEHALF OF THE SECRETARY OF STATE FOR THE HOME DEPARTMENT
Act: McBrearty QC, Irvine; McGill & Co Solicitors
Alt: Johnston QC, Komorowski; Office of the Advocate General
1 April 2016
 The petitioner, Shelley Elizabeth Romein, has applied for registration as a British citizen pursuant to section 4C of the British Nationality Act 1981, as amended by the Citizenship and Immigration Act 2009. The respondent, the Secretary of State for the Home Department, by a decision intimated on 20 June 2013, refused that application. On 18 September 2013 the respondent decided to maintain her previous decision. By way of application for judicial review the petitioner seeks reduction of these decisions and certain declarators.
 The petitioner, who was born in the United States on 16 June 1978, claims British citizenship through descent from her mother. The petitioner’s father was a citizen of the United States. The petitioner is a United States citizen by virtue of her birth. However, the petitioner’s mother, who was born in South Africa on 16 February 1948, is a British citizen by virtue of her father having been born in the United Kingdom. The petitioner’s mother was in South Africa at a time when she was pregnant with the petitioner. The petitioner avers that while her mother was in South Africa she contacted the British consulate in Johannesburg enquiring about the possibility of securing British citizenship for her then unborn child. The petitioner was informed by a consular official that registration of the forthcoming child’s birth would serve no purpose, as nationality could only be passed through the male line. As a consequence of that advice, the petitioner’s mother did not register her birth, when that event occurred, with the British consulate.
 On these averments, which the petitioner offers to prove, and on a proper construction of section 4C of the 1981 Act, the petitioner claims that she is entitled to be registered as a British citizen and therefore that the respondent’s decision of 20 June 2013 to refuse her registration was unlawful. The Lord Ordinary has rejected that claim and upheld the decision of the respondent, and this on the basis that the petitioner’s proposed construction of the relevant statutory provisions was flawed. The petitioner now reclaims. If the petitioner’s primary argument were not to be made out then other lines of argument might be available to her but for present purposes this court is only concerned with the proper construction of section 4C.
 The leading textbook on nationality law describes section 4C as “a dense and at times impenetrable piece of drafting” (Fransman, Fransman’s British Nationality Law (3rd edit) para 220.127.116.11). Nothing in our experience of endeavouring to find what must be taken to be the intended meaning of this provision would lead us to disagree with that characterization. It is however our duty to penetrate even the apparently impenetrable. Having done so to the best of our ability, we have concluded, for the reasons set out below, that the petitioner’s proposed construction of section 4C is to be preferred over that proposed by the respondent. We intend therefore to recall the Lord Ordinary’s interlocutor of 22 January 2015 and reduce the decisions complained of. It may also be appropriate to grant a declarator but perhaps not in the precise terms sought in the petition. We shall accordingly appoint the matter to be brought out by order when, in the absence of agreement between the parties, the appropriate orders consequent upon the terms of this opinion can be discussed.
The historical background
 Counsel for the petitioner, like, in his turn, counsel for the respondent, adopted his written note of argument but, having acknowledged that the reclaiming motion turned on the construction of section 4C of the 1981 Act, he began his submissions with a review of the legislative history of what is now British citizenship and, in particular, the acquisition of citizenship by descent from a parent who was not born in the United Kingdom or other British possession. His starting point was the British Nationality and Status of Aliens Act 1914.
 Section 1(1) of the 1914 Act deems to be “natural-born British subjects” persons born: (a) within His Majesty’s dominions and allegiance; (b) out of His Majesty’s dominions and allegiance but whose father fulfils any of five specified conditions; or (c) on board a British ship. The wife of a British subject is deemed by section 10 of the Act to be a British subject, but otherwise becoming a British subject depends upon naturalization as provided for by Part II of the Act. A feature of section 1(1)(b) (and, indeed, section 10) is gender discrimination. A person shall be deemed to be a natural-born British subject if the person’s father fulfils any of the specified conditions. That the person’s mother fulfils the conditions is neither here nor there.
 The section 1(1)(b) condition to be fulfilled by the British subject father if his child is to be deemed a natural-born British subject which is of particular interest, is (v) and that is:
“[the person’s] birth was registered at a British consulate within one year or in special circumstances, with the consent of the Secretary of State, two years after its occurrence ...”
Counsel for the petitioner pointed to the feature that a person becomes a British subject by virtue of section 1(1)(b)(v) of the 1914 Act by reason of a step taken by the person’s parent. It does not depend upon an exercise of discretion by the Secretary of State. This is in contrast to the process whereby an alien may be naturalized in terms of section 2. In such a case the alien must make an application and the Secretary of State must be satisfied of a number of things, some of which are quite subjective, for example that the alien is of good character and has an adequate knowledge of the English language. If the Secretary of State is so satisfied he may grant a certificate of naturalization. The alien must swear an oath of allegiance before the certificate of naturalization takes effect. Provision is made by section 19(1)(a) for regulations in respect of the registration of certificates of naturalization.
 Section 1(1)(b)(v) of the 1914 Act was repealed by section 1(1) of the British Nationality and Status of Aliens Act 1943. It was replaced by section 1(2) of the 1943 Act which made some alteration to the relevant time limit but again provided that a person born outside His Majesty’s dominions whose father was at the time of the birth a British subject shall be deemed to be a natural-born British subject provided that the person’s birth is registered at a British consulate.
 On its commencement on 1 January 1949 the British Nationality Act 1948 effected a more radical reshaping of British nationality. It introduced the concept of a citizen of the United Kingdom and Colonies, having, by virtue of that citizenship, the status of a British subject. The routes to citizenship are indicated by the cross-headings in Part II of the Act: citizenship by birth or descent; citizenship by registration (of citizens of specified countries, of wives and of minors); citizenship by naturalization; and citizenship by incorporation of territory. Citizenship by birth is provided for, in straightforward terms, by section 4. Subject to two limited provisos (that the father is not the envoy of a foreign power or enemy alien) any person born within the United Kingdom and Colonies shall be a citizen of the United Kingdom and Colonies. Citizenship by descent is a little more complicated. The relevant provision is section 5. The focus of the present petition and the reclaiming motion is citizenship by descent where the birth was in a foreign country but was registered in a consulate, which in the 1948 Act is provided for by subsection(1)(b) but it is convenient to reproduce section 5 in its full terms:
“5 Citizenship by descent
(1) Subject to the provisions of this section, a person born after the commencement of this act shall be a citizen of the United Kingdom and Colonies by descent if his father is a citizen of the United Kingdom and Colonies at the time of the birth:
Provided that if the father of such a person is a citizen of the United Kingdom and Colonies by descent only, that person shall not be a citizen of the United Kingdom and Colonies by virtue of this section unless
(a) that person is born or his father was born in a protectorate, protected state, mandated territory or trust territory or any place in a foreign country where by treaty, capitulation, grant, usage, sufferance, or other lawful means, His Majesty then has or had jurisdiction over British subjects ; or
(b) that person’s birth having occurred in a place in a foreign country other than a place such as is mentioned in the last foregoing paragraph, the birth is registered at a United Kingdom consulate within one year of its occurrence, or, with the permission of the Secretary of State later;
(c) that person's father is, at the time of the birth, in Crown service under His Majesty's government in the United Kingdom ; or
(d) that person is born in any country mentioned in subsection (3) of section one of this Act in which a citizenship law has then taken effect and does not become a citizen thereof on birth.
(2) If the Secretary of State so directs a birth shall be deemed for the purposes of this section to have been registered with his permission notwithstanding that his permission was not obtained before the registration.”
Thus, the structure of section 5(1) is to begin with the statement that a person shall be a citizen by descent if his father is a citizen. That is then subject to a proviso: if the father himself was a citizen by descent only, the person will not be a citizen. However, the proviso is subject to four factual exceptions: (a), (b), (c) and (d). If any one of the exceptions applies to the facts of the person’s case, then he shall be a citizen by descent despite his father also being a citizen only by descent.
 The blatant gender discrimination which was a feature of the 1914 Act was accordingly retained in section 5 of the 1948 Act. It can also be seen in other provisions of the 1948 Act, for example in section 12(2). As far as consular registration is concerned this was underlined by the terms of the Registration of Births and Deaths (Consular Officers) Regulations 1948 (No 2837). Regulation 2(1) provided for the keeping of a register of births of citizens of the United Kingdom and Colonies born after 1 January 1949, by way of Form A in the Schedule, which included under column 6:
“Rank, profession or occupation of father and claim to citizenship of the United Kingdom and colonies” (emphasis added)
To this there was a note in these terms:
“To be inserted as fully as possible, followed by full particulars of his claim to citizenship of the United Kingdom and colonies”.
Regulation 5(4) of the 1948 Regulations provided:
“In every case the consular officer must satisfy himself fully that the national status of the person whose birth or death he is requested to register is such that the registration could properly be effected under these Regulations.”
Thus, the intended effect of the 1948 Regulations, operating in conjunction with the 1948 Act, was that the birth of a child abroad to a citizen of the United Kingdom and Colonies mother by descent could not be registered because that child at that time could have no claim to citizenship by being the child of its mother.
 Some 30 years passed before any formal step was taken to address the disparity in the treatment of mothers when compared with the treatment of fathers. The step was by way of a statement in Parliament by the then Secretary of State for the Home Department, Mr Merlyn Rees, on 7 February 1979, as to how he would exercise the discretion conferred by section 7(1) of the 1948 Act as to the registration, on an application having been made, of a minor child of a citizen of the United Kingdom and Colonies as a citizen of the United Kingdom and Colonies. The Secretary of State was asked what action he proposed to take to help mothers born in the United Kingdom who could not transmit citizenship to their children born overseas in the way that men could. He responded:
“I have decided to make some alterations to the general policy in dealing with applications by women who were born in the United Kingdom and whose children born overseas are still minors. The practice hitherto has been to refuse registration if it appeared that the child was likely to live overseas or if, when the child was living in this country, the father had taken no steps to seek out citizenship for himself.
In future, registration will not be refused on those grounds and a woman born in the United Kingdom will normally be able to have her child registered ...
The whole question of transmission of citizenship in the female line will be a matter to be dealt with in future nationality legislation.”
However, inherent within the Secretary of State’s policy were two limitations: first, as it related only to minors it therefore extended only to persons born after February 1961, and, second, it related only to mothers who were born in the United Kingdom.
 As foreshadowed in the Secretary of State’s statement, the question of transmission of citizenship in the female line was addressed in the next major piece of relevant legislation. This was the British Nationality Act 1981 which came into force on 1 January 1983. While it became more tightly controlled, acquisition of citizenship by descent, acquisition by birth, and acquisition by registration of minors were provided for in terms which referred to the father or mother of the person concerned (see 1981 Act sections 1 to 3). However, despite the move towards gender neutrality, where the claim to British citizenship depended on the citizenship of a person’s parent, section 9 made transitional provision in respect of a person born in a foreign country within five years of commencement of the 1981 Act whose father fulfilled certain requirements.
 The Rees policy became spent after 31 December 2000, 18 years after the birth of the last person to be born prior to the commencement date of the 1981 Act (those born after 1 January 1983 being governed by the 1981 Act). Meanwhile, on 7 April 1986, the United Kingdom had ratified the United Nations Convention on the Elimination of All Forms of Discrimination Against Women (“CEDAW”). Article 9.2 of CEDAW is in these terms:
“States Parties shall grant women equal rights with men with respect to the nationality of their children.”
 With effect from 30 April 2003 the 1981 Act was amended to include a new section 4C. It was inserted by section 13 of the Nationality Immigration and Asylum Act 2002. Section 4C in this its first version or first enactment (we have not yet come to the provision which requires to be construed) was in the following terms:
“4C Acquisition by registration: certain persons born between 1961 and 1983
(1) A person is entitled to be registered as a British citizen if -
(a) he applies for registration under this section, and
(b) he satisfies each of the following conditions.
(2) The first condition is that the applicant was born after 7th February 1961 and before 1st January 1983.
(3) The second condition is that the applicant would at some time before 1st January 1983 have become a citizen of the United Kingdom and Colonies by virtue of section 5 of the British Nationality Act 1948 (c. 56) if that section had provided for citizenship by descent from a mother in the same terms as it provided for citizenship by descent from a father.
(4) The third condition is that immediately before 1st January 1983 the applicant would have had the right of abode in the United Kingdom by virtue of section 2 of the Immigration Act 1971 (c. 77) had he become a citizen of the United Kingdom and Colonies as described in subsection (3) above.”
As will be apparent, section 4C looks to be directed at those persons who might have benefited from the Rees policy of discretionary registration as citizens of children born overseas of mother who had been born in the United Kingdom and who had not reached the age of 18 as at the date of the ministerial statement or who were born subsequently to it but before commencement of the 1981 Act and its different provisions for acquisition of citizenship by registration. Like the Rees policy it is intended to provide what Fransman at para 17.7.1 describes as an antidote to nationality law’s long-standing gender discrimination. The explanatory note to section 13 of the 2002 Act describes the function of the new section as conferring an entitlement to registration as a British citizen on persons born between 7 February 1961 and 1 January 1983 who, but for the inability (at that time) of women to pass on their citizenship, would have acquired British citizenship automatically when the 1981 Act came into force on the latter of those two dates.
 However, and this is why the petitioner’s counsel made reference to the first enactment of section 4C although it is not the provision by which the petitioner’s claim to citizenship is to be judged, there is, according to counsel, a wider construction of the first enactment of 4C than that suggested by the explanatory notes. Section 4C is not limited, as the Rees policy was, to mothers born in the United Kingdom. Moreover, it grants an entitlement to registration as a British citizen on application if before 1 January 1983 the applicant:
“would have become a citizen of the United Kingdom and Colonies by virtue of section 5 of the [1948 Act] if that section had provided for citizenship by descent from a mother in the same terms as it provided for citizenship by descent from a father” (emphasis added)
By virtue of section 5 of the 1948 Act one means whereby a person might have become a citizen by descent from a father (when the father himself was a citizen “by descent only”) was by consular registration of the birth as provided for by subsection (1)(b). The effect of section 4C in its first version, argued the petitioner’s counsel, was to entitle an applicant born before 1 January 1983 to citizenship as if section 5 of the 1948 Act “had provided for citizenship by descent from a mother in the same terms as it provided for citizenship by descent from a father”. Thus, so counsel submitted, if an otherwise qualified applicant (born in a foreign country before 1 January 1983 Act of a British citizen by descent mother) could establish as a matter of fact that he or she would have become a citizen of the United Kingdom and Colonies by virtue of consular registration as provided by section 5(1)(b) of the 1948 Act, then he or she would have been entitled to registration as a British citizen. The “would have become” question was a purely factual one, and accordingly justiciable before the court should that be necessary: R (Harrison) v Secretary of State for the Home Department  INLR 284.
 We shall leave the argument on the proper construction of the first version of section 4C there; it was merely counsel’s ranging shot before addressing the matter upon which his client’s application turns, the proper construction of section 4C as subsequently re-enacted by section 45(3) of the 2009 Act (the second enactment), a provision which came into force on 13 January 2010.
The provision to be construed: the second enactment of section 4C of the 1981 Act
 The second enactment of section 4C is in the following terms:
“4C Acquisition by registration: certain persons born between 1961 and 1983
(1) A person is entitled to be registered as a British citizen if—
(a) he applies for registration under this section, and
(b) he satisfies each of the following conditions.
(2) The first condition is that the applicant was born before 1st January 1983.
(3) The second condition is that the applicant would at some time before 1st January 1983 have become a citizen of the United Kingdom and Colonies—
(a) under section 5 of, or paragraph 3 of Schedule 3 to, the 1948 Act if assumption A had applied,
(b) under section 12(3), (4) or (5) of that Act if assumption B had applied and as a result of its application the applicant would have been a British subject immediately before 1st January 1949, or
(c) under section 12(2) of that Act if one or both of the following had applied—
(i) assumption A had applied;
(ii) assumption B had applied and as a result of its application the applicant would have been a British subject immediately before 1st January 1949.
(3A) Assumption A is that—
(a) section 5 or 12(2) of, or paragraph 3 of Schedule 3 to, the 1948 Act (as the case may be) provided for citizenship by descent from a mother in the same terms as it provided for citizenship by descent from a father, and
(b) references in that provision to a father were references to the applicant's mother.
(3B) Assumption B is that—
(a) a provision of the law at some time before 1st January 1949 which provided for a nationality status to be acquired by descent from a father provided in the same terms for its acquisition by descent from a mother, and
(b) references in that provision to a father were references to the applicant's mother.
(3C) For the purposes of subsection (3B), a nationality status is acquired by a person (“P”) by descent where its acquisition—
(a) depends, amongst other things, on the nationality status of one or both of P's parents, and
(b) does not depend upon an application being made for P's registration as a person who has the status in question.
(3D) For the purposes of subsection (3), it is not to be assumed that any registration or other requirements of the provisions mentioned in that subsection or in subsection (3B) were met.
(4) The third condition is that immediately before 1st January 1983 the applicant would have had the right of abode in the United Kingdom by virtue of section 2 of the Immigration Act 1971 (c. 77) had he become a citizen of the United Kingdom and Colonies as described in subsection (3) above.
(5) For the purposes of the interpretation of section 5 of the 1948 Act in its application in the case of assumption A to a case of descent from a mother, the reference in the proviso to subsection (1) of that section to ‘a citizen of the United Kingdom and Colonies by descent only’ includes a reference to a female person who became a citizen of the United Kingdom and Colonies by virtue of—
(a) section 12(2), (4) or (6) only of the 1948 Act,
(b) section 13(2) of that Act,
(c) paragraph 3 of Schedule 3 to that Act, or
(d) section 1(1)(a) or (c) of the British Nationality (No. 2) Act 1964.”
Section 4C therefore confers an entitlement to registration as a British citizen if an applicant can meet all of three conditions. The first and third conditions are exactly the same in the second enactment as they were in the first enactment. They are not in issue. What is in issue is the second condition, as it falls to be interpreted on a proper construction of subsections (3) to (3D).
 The petitioner’s construction of subsections (3) to (3D) of section 4C is that the meaning of the second enactment is the same as that which counsel had argued was the meaning of the first enactment as far as the retrospective effect of the consular registration provisions of section 5 of the 1948 Act is concerned. The critical wording has been retained; it is to be assumed, by virtue of assumption A, as set out in subsection (3A), that section 5 of the 1948 Act provided for citizenship by descent from a mother in the same terms as it provided for citizenship by descent from a father. Thus, by virtue of what counsel described as a counterfactual (“if assumption A had applied”) section 5 is given retrospective effect as if it had been entirely gender neutral. However, applying a gender neutral reading to section 5 only gives this petitioner an entitlement to citizenship if paragraph (b) (consular registration) can be invoked as an exception to the general effect of the proviso “if the father [or mother] of such a person ... is a citizen ... by descent only, that person shall not be a citizen ...”. Consular registration requires just that: registration at a consulate; whereas as a matter of historical fact the petitioner’s birth was not registered at a British consulate, whether in Johannesburg or anywhere else. That was the first point taken by the respondent against the petitioner’s contention that section 4C gives her an entitlement to register as a British citizen: her birth was not registered, therefore exception (b) does not apply. In response, the petitioner accepted that the exception to the proviso to section 5(1) upon which she relies required consular registration, but she pointed to the wording of section 4C(3) of the 1981 Act which in addition to giving her the benefit of assumption A, allows her the opportunity of proving that she “would ... have become a citizen”. One way of becoming a citizen was by consular registration if the person’s father was a citizen, albeit by descent only. Section 4C provides a first, and what might be described as a legal, counterfactual: that section 5 of the 1948 Act provided for citizenship by descent from a mother in the same terms as it provided for citizenship by descent from a father. An applicant for citizenship can then, so argued the petitioner, by leading evidence, provide a second counterfactual: what would have been done by the applicant’s parents had the law actually been as the first counterfactual assumes it to have been. On the petitioner’s approach, if the second counterfactual is established on a balance of probabilities as a matter of fact in circumstances where the first counterfactual applies as a matter of law, then the applicant is entitled to be registered as a British citizen.
 Against that proposed reading of section 4C, the respondent presented a second objection: it is inconsistent with subsection (3D) which provides that for the purposes of subsection (3) “it is not to be assumed that any registration or other requirements of the provisions mentioned in that subsection or in subsection (3B) were met”. The argument on behalf of the respondent was that “it is not to be assumed” where it appears in subsection (3D), means that it is impermissible to employ a legal fiction so as to suppose that registration had taken place. In effect, subsection (3D) closes off inquiry as to counterfactual possibilities and therefore as registration had not historically been available (or at least registration in conformity to the statute and relevant regulations had not historically been available) where the child could only rely on its descent from its mother, section 4C(3)(a) had no application to exception (b) to the proviso to section 5(1) of the 1948 Act. According to the respondent, section 4C(3)(a) applied only to exceptions (a), (c) and (d). On the respondent’s approach, subsection (3D) was a statement of irrebuttable fact which limits the scope of assumption A. It is significant that the wording is “it is to be assumed that any registration or other requirements ... were met”, as opposed to “... would have been met”.
 The respondent argued that “assumed” in subsection (3D) must be taken to be a cognate with “Assumption” where that word appears in subsection (3A) and subsection (3B) (setting out assumption A and assumption B respectively). Subsections (3A) and (3B) are deeming provisions; they set out incontrovertible assumptions which must be made. Given its close linguistic and contextual connection, “assumed” in subsection (3D) should be given the same construction. The point is clearly articulated by Turner J (who found it significant) in his judgment in Navarro v Secretary of State for the Home Department  EWHC 557:
“In ordinary usage, an assumption can either be (i) an immutable premise or (ii) a working hypothesis capable of being proved wrong. In the context of section 4C assumptions A and B are clearly intended to be in category (i). They are not susceptible to rebuttal in any circumstances. Thus where the cognate ‘assumed’ is deployed within subsection (3D) it is reasonable to assume that Parliament did not intend to give the concept a different meaning within the same statutory framework.”
Counsel for the petitioner had an answer to the subsection (3D) point, but before turning to that, it is of interest to consider the consequence if counsel for the respondent was right when he said that (3D) was a statement of fact reducing the scope of assumption A with another equally incontrovertible assumption. What, in terms of subsection (3D) is “not to be assumed” is that “For the purposes of subsection (3) ... any registration or other requirements of the provisions mentioned in [subsection (3)] or in subsection (3B) were met”. The “provisions mentioned” in the two subsections are: section 5, section 12(2) to (5) of, and paragraph 3 of Schedule 3 to the 1948 Act; and “a provision of the law at some time before 1 January 1949 which provided for a nationality status to be acquired from a father.” When one looks at “the provisions mentioned” one sees that they provide for the acquisition of citizenship depending upon whether certain factual criteria obtain: place of birth, father’s status as a British subject whether by place of birth or father having been granted a certificate of naturalization (prior to the commencement of the 1948 Act), father’s status as a citizen of the United Kingdom and Colonies (after commencement of the 1948 Act), father’s Crown service, and marriage to a British subject. At first blush these factual criteria might be thought to be “other requirements of the provisions”, but were that so, and were the respondent correct in construing “assumed” in subsection (3D) as establishing what Turner J in Navarro described as an immutable premise, then section 4C(3) would be deprived of all effect whatsoever. Counsel for the respondent recognised that. He accordingly offered a narrower construction of “other requirements” as confined to things which required to be done in order to secure citizenship by descent, as opposed to events or states of affairs, such as a person’s father being in Crown service. An example of something requiring to be done, other than registration, (and perhaps the only example) would be an application for the inclusion of a child in a certificate of naturalisation in terms of section 5 of the 1914 Act. Despite the paucity of examples, counsel for the respondent pointed to the textual context. The phrase under consideration is “registration or other requirements of the provisions”. A construction ejusdem generis would therefore suggest that “other requirements” was a reference to things similar in character to registration, in other words administrative or clerical things which required to be done if citizenship was to be acquired. While that avoids a nonsensical outcome while preserving the respondent’s construction of “assumed”, it is hardly convincing. The natural meaning of “other requirements of the provisions” is everything else that the provisions require.
 The answer provided by counsel for the petitioner to the respondent’s subsection (3D) point was succinct. It was unimportant whether “assumed” was intended as giving rise to an immutable premise or a working hypothesis because, whichever it was, it was “not to be assumed”. Therefore, as nothing was to be assumed in relation to consular registration, it was open to an applicant to prove (the onus being on him or her) that had the law been as assumption A required it to be assumed it was, the applicant’s birth would have been registered at a consulate. That is what the petitioner was offering to prove. We observe that on the petitioner’s approach to subsection (3D) there is no difficulty about giving the expression “other requirements of the provisions” what we would see to be its natural meaning.
 We are with the petitioner. Contrary to what we understand to have been conceded to the Lord Ordinary, it is the respondent’s construction of subsection (3D) with the unnaturally narrow meaning which it gives to “requirements” which we would see to be strained rather than the petitioner’s construction of the subsection, which seems to us to be quite straightforward. However, for the petitioner to be entitled to be registered as a British citizen by virtue of section 4C she must satisfy the condition that she “would ... have become a citizen... under section 5 of ... the 1948 Act.” We have set out the petitioner’s position on that when discussing the first enactment: section 4C allows her to prove this as a second and evidence-based counterfactual. Not so, submitted counsel for the respondent advancing his third and fourth objections to the petitioner’s construction. “Would ... have become ... under section 5” indicates certainty. What the phrase means is that the applicant would necessarily have become a citizen by operation of law independent of anyone’s actions. Moreover, the petitioner’s construction would make the provision unworkable. It would be impossible to test or properly verify an assertion that the birth would have been registered (a consideration which influenced the Lord Ordinary). Where a decision on nationality was to be made depending on potentially uncertain circumstances the expectation would be that the statute would use the formula “the Secretary of State is satisfied”, as in section 4B(2).
 We see the force of the contention that, taken in isolation, the phrase “would ... have become ... under [a particular statutory provision]” is suggestive of the necessary legal consequence of some antecedent state of affairs. That reading fits well with section 12(2) to (5) of the 1948 Act where each of the subsections referred to in section 4C(3) of the 1981 Act provides that either a “person” or “woman”, “who was a British subject immediately before the date of the commencement of this Act, shall on that date become a citizen of the United Kingdom and Colonies”. It fits less well with section 5. Section 5 looks to the situation of “a person born after the commencement of this Act”. The section provides, through a structure of exceptions to the proviso, that such a person, born of a citizen of the United Kingdom and Colonies father, albeit a citizen by descent, “shall be a citizen of the United Kingdom and Colonies” if one or other of the set of circumstances identified in exceptions (a), (b), (c) and (d) apply. However, because that is what the subsection provides in terms, for the purposes of section 4C(3) it must be taken to be conceptually possible that an applicant would “have become” a citizen “under section 5” had the 1948 Act provided for citizenship by descent from a mother. According to the respondent, that is so but only by virtue of the paragraph (a), (c) and (d) exceptions, not by virtue of the paragraph (b) exception.
 We are unable to accept this distinction. Once the section 5 exceptions, together with a parent’s citizenship, are taken to be ways by which a person may become a citizen we cannot see a satisfactory basis for distinguishing among the exceptions on the basis of certainty of outcome. Each of the exceptions is a set of factual circumstances which, if disputed, would have to be established on a balance of probabilities as a matter of fact. True, with the (a), (c) and (d) exceptions what is in issue are historical facts (things that have actually happened), a mother’s Crown service at the relevant time, for example; while with exception (b) what is in issue is counterfactual, what it is likely the parents of the applicant would have decided to do and would have done had the law been as assumption A requires it to be assumed that it was. However, where there is no provision which expressly excludes exception (b) as a way by which an applicant “would ... have become” a citizen, we do not see that it can be excluded by implication. That it might be difficult for an applicant to prove that exception (b) would have applied to his or her case does not have the result that the construction contended for by the petitioner is unworkable. Courts of law are very familiar in a variety of different contexts with deciding what would have happened had events or circumstances been different than they were, even where doing so requires coming to a view as to how the people involved were likely to have acted. We are simply not persuaded by the respondent’s submission that where entitlement to citizenship depends on matters of uncertain fact, one would expect to find the formulation “the Secretary of State is satisfied that the applicant would ... have become a citizen of the United Kingdom and Colonies”. No doubt the statute might have been framed in these terms (section 6(3) of the 1943 Act provides an example of a similar provision) but, as the petitioner submitted, that would have been to shift what ex hypothesi is the meaning of the provision from an entitlement to citizenship to a recognition of citizenship at the discretion of the Secretary of State.
 The respondent’s fifth reason for rejecting the petitioner’s proposed construction of section 4C was that it would result in unequal treatment for someone in a comparable position to the petitioner, but born between 1919 and 1948. The argument was as follows. Similar provision to section 5 of the 1948 Act was made for those born between 1915 and 1948 by virtue of section 1(b)(v) of the 1914 Act as amended by the British Nationality and Status of Aliens Act 1922 and section 1(2)(b) of the British Nationality and Status of Aliens Act 1943. Under each Act, a person whose father was a British subject by descent became a British subject if his or her birth was registered at a consulate. Section 19(1)(c) of the 1914 Act allowed for regulations to be made providing for consular registration of births, but only of “British subjects”. Therefore, to acquire citizenship by virtue of section 1(b)(v) of the 1914 Act or section 1(2) of the 1943 Act, a person required to have his or her birth registered at a consulate, registration being of the person’s status as a British subject. However, section 4C(3C)(b) of the 1981 Act directs, put shortly, that measures providing for citizenship by descent were not to be treated as covering children of mothers who were British nationals where the provision depended on “an application being made for … [that person’s] registration as a person who has the status in question.” It follows that someone born between 1915 and 1949, whose mother was a British subject, who would have become a British subject if their father was a British subject and there had been consular registration of the birth, would not benefit from section 4C of the 1981 Act. This, it was argued on behalf of the respondent, was an indication that the petitioner’s construction was not correct; Parliament could not have intended to treat differently persons born in otherwise identical circumstances between 1919 and 1948, when compared with those born between 1949 and 1982.
 We have been persuaded by the petitioner that no inconsistency of treatment such as is posited by the respondent arises on a proper construction of the relevant provisions in relation to persons born between 1919 and 1948. What section 4C(3C) is concerned with is a situation where in terms of the pre-1949 legislation the acquisition of nationality depended on the nationality status of a parent but did not depend upon “an application being made for ... registration”. The inclusion of “application” was significant. As counsel for the petitioner pointed out at the beginning of his review of the historical background, section 1(1)(b)(v) of the 1914 Act, which provides for consular registration, makes no reference to “application”. The point is not simply textual. Where provision is made for a person to apply or for an application to be made, that indicates that what is sought may be refused or, at the very least, a decision must be made to grant what is sought. By contrast, consular registration, where timeous, is a matter of right. There are provisions of the 1914 Act relating to the acquisition of nationality by descent which fit with a requirement for an application and for registration to which section 4C (3C) may be taken to apply. Section 2 provides for an alien making an application for a certificate of naturalization. Section 5 provides for including the name of any child of the alien in the certificate. Section 19 provides for the making of regulations as to, among other things, the registration of certificates. Thus, because the relevant provision for consular registration makes no reference to application, section 4C(3C)(b) does not prevent pre-1949 acquisition of citizenship by descent and consular registration, being “a nationality status ... acquired ... by descent” for the purposes of subsection (3B). The respondent’s reply was to recognize that a meaning had to be found for “application” where it appeared in section 4C(3C)(b) but to argue that the need for an application was implicit in presenting oneself at or addressing oneself to a consulate with a view to the registration of a birth. We are not persuaded. We accept that as a matter of common parlance one might consider “apply to register” as an appropriate expression to describe the necessary step of bringing what one wished to register to the attention of the registration authority, thereby permitting the next step being the interaction which might be described as “registration” and that therefore before it can be said of a birth that it “was registered”, which is the wording of section 1(b)(v) of the 1914 Act, there must in that sense have been an application to register. However, where the context is one of interaction with an administrative authority with a view to achieve a particular result, “application” or its cognate “apply”, have well understood and specific meanings which are different from “registration” or “register”. As counsel for the petitioner submitted, an “application” is a request for a power to be exercised in one’s favour. The critical act is that by the authority to which the application is made. Registration, on the other hand, is a matter of right (or perhaps duty); it is the act of the person who has addressed himself to the administrative authority. Where “application” appears in an act of Parliament the expectation is that it is being used in the more formal sense of a request for a power to be exercised in one’s favour. Also favouring the petitioner’s construction of section 4C(3C) over that of the respondent is that if the meaning of the subsection was as the respondent would have it, there would be no need for section (3D) to include “registration ... requirements of the provisions mentioned ... in subsection (3B)” because if the respondent’s construction of section 4C(3C) were correct, there would be no relevant “registration ... requirements of the provisions mentioned ... in subsection (3B)”; they would have been excluded by subsection (3C)(b).
 In a sixth objection to the petitioner’s construction of section 4C, the respondent pointed to the consequential inconsistency in treatment as between the petitioner and someone in a comparable position to the petitioner, but born between 1983 and 1987. This is because section 9 of the 1981 Act specifically continued the discriminatory effect of section 5 of the 1948 Act by allowing the acquisition of citizenship by virtue of consular registration and descent from a father (but not mother) for a period of five years after commencement of the 1981 Act. According to the respondent that was a factor pointing away from the petitioner’s construction. The petitioner’s response was to accept the inconsistency but to explain it as a deliberate decision of Parliament which was in line with the terms in which the United Kingdom had ratified CEDAW on 7 April 1986. That requires elaboration.
 Parties were agreed that in construing an Act of Parliament it is relevant to have regard to the United Kingdom’s obligations under international treaties. Ratification of a treaty is an act of the executive in exercise of a Crown prerogative, but in interpreting a statute it is to be presumed that Parliament did not intend to act in breach of international law and in particular did not intend to legislate in contravention of treaty obligations, and therefore if one meaning is consonant with such obligations and another is not, it is the meaning which is consonant which is to be preferred: Salomon v Custom and Excise Comrs  2 QB 116 Diplock LJ at 143; Bennion, Bennion on Statutory Interpretation (6th edit) p745. Here the treaty or convention in question is CEDAW, adopted by the United Nations General Assembly on 18 December 1979 and ratified by the United Kingdom on 7 April 1986. Of particular importance is article 9.2 which provides that parties shall grant women equal rights with men with respect to the nationality of their children. The petitioner argues that her preferred construction of section 4C more nearly provides for the equal rights of women with respect to the nationality of their children than the respondent’s preferred construction and that therefore she can rely on the presumption that Parliament intended to legislate in accordance with the United Kingdom’s international obligations, but for the purpose of explaining the apparent anomaly arising from section 9 she points to what precisely it was that the United Kingdom signed up to when it ratified the convention.
 On ratification the United Kingdom stated certain reservations to CEDAW, so limiting the extent to which it was bound by it. One reservation was specific to article 9:
“The British Nationality Act 1981, which was brought into force with effect from January 1983, is based on principles which do not allow of any discrimination against women within the meaning of Article 1 as regards acquisition, change or retention of their nationality or as regards the nationality of their children. The United Kingdom's acceptance of Article 9 shall not, however, be taken to invalidate the continuation of certain temporary or transitional provisions which will continue in force beyond that date.”
Thus, as the petitioner submitted, her construction, when taken with section 9, may give rise to an inequality of treatment as between those born between 1983 and 1987 and those born between 1949 and 1982 but the United Kingdom had stated that it reserved its right to maintain inequalities over a transitional period and Parliament in enacting subsequent legislation may be taken to be aware of that.
 Had we found ourselves in doubt as to which of the petitioner’s or the respondent’s constructions should be preferred, we would have regarded article 9.2 as weighing on the petitioner’s side of the balance. Both parties were agreed that a purpose of the 1981 Act, as subsequently amended in terms of both the enactments of section 4C, was to reduce gender discrimination in the acquisition of citizenship. We accept that achieving that purpose retrospectively may introduce practical difficulties and that Parliament may reasonably have accepted an imperfect legislative outcome. Nevertheless, given the accepted purpose, as reinforced by the international obligation, we would see that the intention of Parliament is more likely to have been to achieve a greater rather than a lesser degree of reduction in discrimination.
 Two other external aids to construction were drawn to our attention in the course of the discussion. The first was a statement in Parliament by the Home Office Minister, Lord Filkin, on 31 October 2002, explaining the purpose of what became the first enactment of section 4C (HL Deb, vol 640 col 295). It was relied on in the respondent’s note of argument but counsel for the respondent departed from any such reliance in the course of submissions. The second external aid was relied on by the petitioner. It was a parliamentary statement contained in a letter from Lord Brett, dated 20 March 2009, which was written to Lord Avebury but copied to all Members of the House and deposited in the library. Lord Brett was the Government minister responsible for what would become the second enactment. In the letter of 20 March 2009, which was written in the context of a proposed amendment to what would become subsection (3D), Lord Brett noted as follows:
“In our recent discussions it has been suggested that mothers unable to transmit their citizenship status under the [1948 Act] may not have taken action, such as consular registration of their child born overseas, because they would divine no practical benefit from doing so. However, some women who gave birth to children in such circumstances did in fact consularly register their child: that child would now be caught by the parametres [sic] of section 4C. We do not think it appropriate to make assumptions about what the parent would have done if the law had been framed differently: we continue to believe it appropriate to focus on the available facts and evidence rather than make assumptions on behalf of parents, many of whom may now be deceased.”
Counsel for the petitioner referred to the opinion of Lord Hope in Gow v Grant 2013 SC (UKSC) 1 at para 29 for the proposition that a letter was one way in which the promoter of legislation might identify what he intended by it and so become part of material it was permissible to consider when construing statute by virtue of the decision in Pepper v Hart  AC 593. We do not propose to follow counsel’s invitation and give weight to the ministerial letter. First, although the process has not been entirely straightforward we consider that we have arrived at the proper construction of the relevant provisions by the primary route, which is by examination of the text and attribution of its natural meaning. It is therefore unnecessary to consider external material. Second, we do not regard the precise meaning of the minister’s letter to be clear. He introduces the information that despite the terms of the relevant statutes and regulations, some mothers did succeed in registering the births of children at British consulates. He suggests that these irregular registrations might be retrospectively validated by operation of section 4C but not only does he not explain why, he does not make clear whether or not he considers that only such irregular registrations are covered. What he goes on to say about “assumptions about what the parent would have done” might be read as supporting the petitioner’s construction of the section but, again, we do not find this sufficiently clearly stated to warrant the letter being relied on.
 We can now summarise our overall approach. There is no good reason to limit the scope of section 4C(3) as first enacted in 2002, and it is inherently unlikely that the revised version in 2009 was intended to reintroduce aspects of gender discrimination previously discarded. On the contrary, the intention in 2009 was to broaden the sweep of section 4C, for example to cover other routes to British citizenship beyond section 5 of the 1948 Act.
 The terms of section 4C as enacted in 2009 provide for a successful application if, amongst other things, it can be proved that the birth of a person would have been registered had section 5 of the 1948 Act provided for citizenship by descent from a mother or a father in equal terms. Subsection (3D) is framed in the negative. It excludes things, in particular there are to be no assumptions made in favour of the application. For example, as Fransman notes (paragraph 18.104.22.168), there is to be no assumption that a British mother by descent would have registered her child’s birth. The provisions could have, but do not prohibit an application based upon the registration provisions in section 5 of the 1948 Act.
 Subsection (3D) simply puts an applicant to proof of his or her claim, in that it is “not to be assumed” that the various criteria for entitlement to citizenship were met. There might be correspondence showing that enquiries were made at the time, but only the mother was a British citizen by descent. In such a case the requirements would be met by proof that registration would have taken place and the applicant would have become a citizen of the United Kingdom and Colonies. On the other hand, a claim might fail because registration would never have taken place in that it would have resulted in loss of citizenship of the place of birth and residence. Or an applicant might be unable to prove that his mother was in Crown service at the relevant time.
 In short, subsection (3D) is designed to ensure success only for those applicants who can show that they would have become citizens of the United Kingdom and Colonies if mothers had been treated in the same way as fathers. Were it otherwise, applicants under section 4C might gain citizenship even though they were not victims of discrimination. Furthermore, in our view, the respondent’s approach to subsection (3D) robs section 4C(3) of all effect, since her interpretation cannot be limited to only some of the requirements of the provision.
 We find ourselves in respectful disagreement with not only the Lord Ordinary but also the learned judge in Navarro. On a proper construction of section 4C(3) the petitioner is entitled to be registered as a British citizen if she can prove that she would have become a citizen of the United Kingdom and Colonies by virtue of section 5 of the 1948 Act if the assumption set out in section 4C(3A) had applied at the relevant time. For completeness we record that the appeal hearing did not address the issues potentially arising under ECHR, since they would be relevant only if the court was against the petitioner on the construction issue. The reclaiming motion will be allowed and the petitioner’s application remitted to the respondent for reconsideration. However, in the meantime we shall put the case out by order for discussion as to the appropriate terms of the court’s interlocutor, including any declaratory orders.