1. Introduction
2. The Right to Procreate
  2.1 Skinner v. Okla.
  2.2 Wiscon. v. Oakley
  2.3 Involuntary Sterilization
  2.4 Kin Selection
  2.5 Marriage
  2.5.1 Anonymous
  2.5.2 Tompkins v. Tompkins
  2.5.3 Williams v. Williams
  2.6 Transgender Marriage
  2.7 Polygamy
  2.8 Prostitution
  In Brief
3. Who Is My Family?
3.1 Family Identity and the Right to Associate with Kin
  3.2 Marriage and the Paternity Presumption
  3.2.1 Jones v. Trojak
  3.2.2 Michael H. v. Gerald D.
  3.2.3 William "TT" v. Siobhan "HH"
3.3 Paternity Estoppel
3.4 Equitable Parenthood
3.5 Duty to Support
  3.6 The Paramour Statute
  3.7 Maternal Transmission of Citizenship
  In Brief
4. Whose Child Is This?
  4.1 The Surrogate Cases
  4.1.1 Johnson v. Calvert
  4.1.2 Belsito v. Clark
  4.2 Shotgun Weddings
  4.2.1 Fairchild v. Fairchild
  4.2.2 Gard v. Gard
  4.2.3 B. v. S.
  In Brief
5. Shopping For Eggs & Sperm
  5.1 Bad Sperm
  5.2 Cryogenic Orphans & Waifs
  5.2.1 Gifts of Sperm
  5.2.2 Who Is My Father?
  In Brief
6. Sexual Orientation
  6.1 The Right to Practice One’s Sexual Orientation
  6.2 Discriminating on the Basis of Sexual Orientation
6.3 Same-sex Adoption
6.4 Same-sex Marriages
  In Brief

3.7.  Maternal transmission of citizenship

An offspring’s genetic information is a composite of its parent since each parent contributes one set of chromosomes to the embryo.  As a result, for the most part, each trait possessed by an offspring is influenced by both a maternal and paternal gene.  There are exceptions to this rule of parity.  Several types of genetic information are transmitted only through one parent – usually the mother.

Mitochondrial information is one example.  Mitochondria, an organelle that produces energy for the cell, contains its own strand of DNA that codes some, but not all, of the information it needs to replicate itself and carry out its physiological processes.  Mammalian offspring inherit their mitochondria from the mother for the simple reason that no viable mitochondria are carried into the egg by the sperm.  The sperm’s only contribution to the egg is its nucleus, and the nuclear genes that reside within it.  It leaves its mitochondria outside, along with its mitochondrial genes.  As a result, the offspring’s only source of mitochondria is the mother’s egg.  Mitochondrial diseases, which are caused by a defect in a mitochondrial gene, are carried exclusively through the maternal line.

Genetic imprinting is another example of genetic information that comes from only one parent.  Individuals inherit, from each parent, a copy of every gene in the genome.  In most cases, each gene is active in the offspring, making its own contribution to the offspring’s phenotype.  There are several dozen genes in the mammalian genome which are an exception to this rule.   In these genes, only one of the two parental alleles is expressed in the offspring.  The other allele is inactivated, behaving as if it were simply not there.  The phenomenon is called “genetic imprinting” because one of the two alleles is “imprinted” with the instruction not to express.  Imprinting is believed to occur when chemical modifications are made to the nucleotides which make up the gene. Many of the imprinted genes are involved in fetal growth and development.  Both maternal and paternal imprinted genes have been identified.  See, e.g., Reik and Walter, Nature Reviews, Genetics, 2:2132, 2001.

Sex-linked inheritance illustrates a third way in which certain genetic information is passed through one parent, but not the other.  A pair of chromosomes, known as the “sex chromosomes,” determine a mammal’s gender.  There are two different sex chromosomes, X and Y.  The X-chromosome is estimated to contain about 1200 genes, while the Y-chromosome contains much fewer, only about 230 genes.  See, e.g., www.wellcome.ac.uk/en/genome. Females are XX and males are XY.  For males who are XY, all the X genes are derived from the mother.  Diseases, such as hemophilia, are coded for by X-chromosome genes.  These are also called X-linked diseases because they are assosciated (“linked”) with the X-chromosome.  They occur more frequently in males because males carry only one copy of the X-linked gene, and if it’s a bad copy, the result is the disease.  Females have two copies of every X-linked gene, and if one copy is defective, they still have a second, good copy to make up for it.

Maternal transmission is not limited to genes.  Certain cultural traits are also transmitted through the maternal side.  In the Jewish religion, for example, offspring from a mixed marriage (e.g. a Jew and a Buddhist) are only Jewish if the mother is also Jewish.  This type of cultural transmission is mirrored in Federal law.   Under U.S. Immigration law §1409,  a child born outside the U.S., and out-of-wedlock, is automatically a U.S. citizen if its mother is a U.S. citizen.  However, a child of a non-citizen mother and a citizen father, born out-of-wedlock and in a foreign country, is not conferred U.S. citizenship until specific actions are taken by its father.  The reason is that, under federal law, citizenship is transmitted maternally when an offspring is born outside the United States.

Why should it be the mother who determines the child’s citizenship?  One reason may reflect the economics of biology.  The mother makes the biggest investment in the child, while the father contributes only his nuclear genes to the child.  Even before fertilization, the mother has created a nutrient rich egg that provides the initial energy to jumpstart embryonic development and keep it going until a more permanent nutrient source is installed.  Once the embryo is implanted into the mother’s uterus, she provides all its energy needs through the placenta, a direct connection between her own and her child’s blood.  Given such a big commitment to the child, shouldn’t she have first dibs on who controls it?  By making the baby’s citizenship the same as the mother’s, it gives her the greater power to keep it with her, and obtain for it the benefits that accompany citizenship.

At the same time, maternal transmission of citizenship reinforces traditional gender roles, while protecting the interest of American society in keeping immigrants outside its borders.  The male is free to disseminate his sperm internationally, impregnating as many women as he chooses, without the risk of a child coming back to him for support.  Any child of an international union between an American man and a foreign woman cannot claim U.S. citizenship, impeding the child’s ability to pursue its father into the United States.  American genes get dispersed all over the world with no economic cost.  The baby stays overseas, unless the Dad takes active measures to bring it with him. 

As well, it could be argued that the maternal rule is a reflection of the sex roles that have arisen from the reproductive differences between the sexes.  Because of the high cost of growing an embryo inside her, the female has focused her efforts on raising the child once it emerges from her.  Since maternity is guaranteed, every ounce of energy she puts into her child is worth it from a gene’s eye perspective.  Maternal investment in progeny is always high for mammals, and females typically are the caregivers for the child.  Giving the baby her citizenship, rather than the father’s, puts baby in the hands of the most competent caretaker.

Tuan Nguyen was born to a Vietnamese mother and American father, but raised in the United States by his father.  Because Tuan was never naturalized as an American citizen, and because his father had never legitimized their relationship, when Tuan was convicted for a felony, he suddenly became eligible for deportation by the INS.  Hoping to avoid the deportation order, Tuan and his father appealed, arguing that §1409 was unconstitutional since it treated men differently than women in violation of the Equal Protection clause.

TUAN ANH NGUYEN AND JOSEPH BOULAIS, PETITIONERS v. IMMIGRATION AND NATURALIZATION SERVICE,

SUPREME COURT OF THE UNITED STATES, 

2001 U.S. LEXIS 4340, June 11, 2001, Decided.

OPINION: JUSTICE KENNEDY delivered the opinion of the Court.

Title 8 U.S.C. § 1409 governs the acquisition of United States citizenship by persons born to one United States citizen parent and one noncitizen parent when the parents are unmarried and the child is born outside of the United States or its possessions. The statute imposes different requirements for the child's acquisition of citizenship depending upon whether the citizen parent is the mother or the father. The question before us is whether the statutory distinction is consistent with the equal protection guarantee embedded in the Due Process Clause of the Fifth Amendment.

I.  Petitioner Tuan Ahn Nguyen was born in Saigon, Vietnam, on September 11, 1969, to copetitioner Joseph Boulais and a Vietnamese citizen. Boulais and Nguyen's mother were not married. Boulais always has been a citizen of the United States, and he was in Vietnam under the employ of a corporation. After he and Nguyen's mother ended their relationship, Nguyen lived for a time with the family of Boulais' new Vietnamese girlfriend. In June 1975, Nguyen, then almost six years of age, came to the United States. He became a lawful permanent resident and was raised in Texas by Boulais.

In 1992, when Nguyen was 22, he pleaded guilty in a Texas state court to two counts of sexual assault on a child. He was sentenced to eight years in prison on each count. Three years later, the United States Immigration and Naturalization Service (INS) initiated deportation proceedings against Nguyen as an alien who had been convicted of two crimes involving moral turpitude, as well as an aggravated felony. See 8 U.S.C. §§ 1227(a)(2)(A)(ii) and (iii) (1994 ed., Supp. IV). Though later he would change his position and argue he was a United States citizen, Nguyen testified at his deportation hearing that he was a citizen of Vietnam. The Immigration Judge found him deportable.

Nguyen appealed to the Board of Immigration of Appeals and, in 1998, while the matter was pending, his father obtained an order of parentage from a state court, based on DNA testing. By this time, Nguyen was 28 years old. The Board dismissed Nguyen's appeal, rejecting his claim to United States citizenship because he had failed to establish compliance with 8 U.S.C. § 1409  (a), which sets forth the requirements for one who was born out of wedlock and abroad to a citizen father and a noncitizen mother.

Nguyen and Boulais appealed to the Court of Appeals for the Fifth Circuit, arguing that § 1409 violates equal protection by providing different rules for attainment of citizenship by children born abroad and out of wedlock depending upon whether the one parent with American citizenship is the mother or the father. The court rejected the constitutional challenge to § 1409(a). 208 F.3d 528, 535 (2000).

II.

The general requirement for acquisition of citizenship by a child born outside the United States and its outlying possessions and to parents who are married, one of whom is a citizen and the other of whom is an alien, is set forth in 8 U.S.C. § 1401(g). The statute provides that the child is also a citizen if, before the birth, the citizen parent had been physically present in the United States for a total of five years, at least two of which were after the parent turned 14 years of age.

As to an individual born under the same circumstances, save that the parents are unwed, § 1409(a) sets forth the following requirements where the father is the citizen parent and the mother is an alien:

"(1) a blood relationship between the person and the father is established by clear and convincing evidence,

"(2) the father had the nationality of the United States at the time of the person's birth,

"(3) the father (unless deceased) has agreed in writing to provide financial support for the person until the person reaches the age of 18 years, and

"(4) while the person is under the age of 18 years --

"(A) the person is legitimated under the law of the person's residence or domicile,

"(B) the father acknowledges paternity of the person in writing under oath, or

"(C) the paternity of the person is established by adjudication of a competent court."

In addition, § 1409(a) incorporates by reference, as to the citizen parent, the residency requirement of § 1401(g).

When the citizen parent of the child born abroad and out of wedlock is the child's mother, the requirements for the transmittal of citizenship are described in § 1409(c):

"(c) Notwithstanding the provision of subsection (a) of this section, a person born, after December 23, 1952, outside the United States and out of wedlock shall be held to have acquired at birth the nationality status of his mother, if the mother had the nationality of the United States at the time of such person's birth, and if the mother had previously been physically present in the United States or one of its outlying possessions for a continuous period of one year."

Section 1409(a) thus imposes a set of requirements on the children of citizen fathers born abroad and out of wedlock to a noncitizen mother that are not imposed under like circumstances when the citizen parent is the mother. All concede the requirements of §§ 1409(a)(3) and (a)(4), relating to a citizen father's acknowledgment of a child while he is under 18, were not satisfied in this case. We need not discuss § 1409(a)(3), however.  …  And in any event, our ruling respecting § 1409(a)(4) is dispositive of the case. As an individual seeking citizenship under § 1409(a) must meet all of its preconditions, the failure to satisfy § 1409(a)(4) renders Nguyen ineligible for citizeship.

III. 

For a gender-based classification to withstand equal protection scrutiny, it must be established "'at least that the [challenged] classification serves "important governmental objectives and that the discriminatory means employed" are "substantially related to the achievement of those objectives."' " United States v. Virginia, 518 U.S. 515, 533, 135 L. Ed. 2d 735, 116 S. Ct. 2264 (1996) (quoting Mississippi Univ. for Women v. Hogan, 458 U.S. 718, 724, 73 L. Ed. 2d 1090, 102 S. Ct. 3331 (1982) in turn quoting Wengler v. Druggists Mut. Ins. Co., 446 U.S. 142, 150, 64 L. Ed. 2d 107, 100 S. Ct. 1540 (1980)). For reasons to follow, we conclude § 1409 satisfies this standard.

The statutory distinction relevant in this case, then, is that § 1409(a)(4) requires one of three affirmative steps to be taken if the citizen parent is the father, but not if the citizen parent is the mother: legitimation; a declaration of paternity under oath by the father; or a court order of paternity. Congress' decision to impose requirements on unmarried fathers that differ from those on unmarried mothers is based on the significant difference between their respective relationships to the potential citizen at the time of birth. Specifically, the imposition of the requirement for a paternal relationship, but not a maternal one, is justified by two important governmental objectives. We discuss each in turn.

A.

The first governmental interest to be served is the importance of assuring that a biological parent-child relationship exists. In the case of the mother, the relation is verifiable from the birth itself. The mother's status is documented in most instances by the birth certificate or hospital records and the witnesses who attest to her having given birth.

In the case of the father, the uncontestable fact is that he need not be present at the birth. If he is present, furthermore, that circumstance is not incontrovertible proof of fatherhood. See Lehr v. Robertson, 463 U.S. 248, 260, n. 16, 77 L. Ed. 2d 614, 103 S. Ct. 2985 (1983) ("' The mother carries and bears the child, and in this sense her parental relationship is clear. The validity of the father's parental claims must be gauged by other measures'" (quoting Caban v. Mohammed, 441 U.S. 380, 397, 60 L. Ed. 2d 297, 99 S. Ct. 1760 (1979) (Stewart, J., dissenting))); Trimble v. Gordon, 430 U.S. 762, 770, 52 L. Ed. 2d 31, 97 S. Ct. 1459 (1977) ("The more serious problems of proving paternity might justify a more demanding standard for illegitimate children claiming under their fathers' estates than that required . . . under their mothers' estates . . . "). Fathers and mothers are not similarly situated with regard to the proof of biological parenthood. The imposition of a different set of rules for making that legal determination with respect to fathers and mothers is neither surprising nor troublesome from a constitutional perspective. Cf. Cleburne v. Cleburne Living Center, Inc., 473 U.S. 432, 439, 87 L. Ed. 2d 313, 105 S. Ct. 3249 (1985) (explaining that the Equal Protection Clause "is essentially a direction that all persons similarly situated should be treated alike"); F. S. Royster Guano Co. v. Virginia, 253 U.S. 412, 415, 64 L. Ed. 989, 40 S. Ct. 560 (1920). Section 1409(a)(4)'s provision of three options for a father seeking to establish paternity -- legitimation, paternity oath, and court order of paternity -- is designed to ensure an acceptable documentation of paternity.

Petitioners argue that the requirement of § 1409(a)(1), that a father provide clear and convincing evidence of parentage, is sufficient to achieve the end of establishing paternity, given the sophistication of modern DNA tests. Brief for Petitioners 21-24. Section 1409(a)(1) does not actually mandate a DNA test, however. The Constitution, moreover, does not require that Congress elect one particular mechanism from among many possible methods of establishing paternity, even if that mechanism arguably might be the most scientifically advanced method. With respect to DNA testing, the expense, reliability, and availability of such testing in various parts of the world may have been of particular concern to Congress. See Miller, supra, at 437 (opinion of STEVENS, J.). The requirement of § 1409(a)(4) represents a reasonable conclusion by the legislature that the satisfaction of one of several alternatives will suffice to establish the blood link between father and child required as a predicate to the child's acquisition of citizenship. Cf. Lehr, supra, at 267-268 (upholding New York statutory requirement that gave mothers of children born out of wedlock notice of an adoption hearing, but only extended that right to fathers who mailed a postcard to a "putative fathers registry"). Given the proof of motherhood that is inherent in birth itself, it is unremarkable that Congress did not require the same affirmative steps of mothers.

Finally, to require Congress to speak without reference to the gender of the parent with regard to its objective of ensuring a blood tie between parent and child would be to insist on a hollow neutrality. As JUSTICE STEVENS pointed out in Miller, Congress could have required both mothers and fathers to prove parenthood within 30 days or, for that matter, 18 years, of the child's birth. 523 U.S. at 436. Given that the mother is always present at birth, but that the father need not be, the facially neutral rule would sometimes require fathers to take additional affirmative steps which would not be required of mothers, whose names will appear on the birth certificate as a result of their presence at the birth, and who will have the benefit of witnesses to the birth to call upon. The issue is not the use of gender specific terms instead of neutral ones. Just as neutral terms can mask discrimination that is unlawful, gender specific terms can mark a permissible distinction. The equal protection question is whether the distinction is lawful. Here, the use of gender specific terms takes into account a biological difference between the parents. The differential treatment is inherent in a sensible statutory scheme, given the unique relationship of the mother to the event of birth.

B.

1.

The second important governmental interest furthered in a substantial manner by § 1409(a)(4) is the determination to ensure that the child and the citizen parent have some demonstrated opportunity or potential to develop not just a relationship that is recognized, as a formal matter, by the law, but one that consists of the real, everyday ties that provide a connection between child and citizen parent and, in turn, the United States. See id. at 438-440 (opinion of STEVENS, J.). In the case of a citizen mother and a child born overseas, the opportunity for a meaningful relationship between citizen parent and child inheres in the very event of birth, an event so often critical to our constitutional and statutory understandings of citizenship. The mother knows that the child is in being and is hers and has an initial point of contact with him. There is at least an opportunity for mother and child to develop a real, meaningful relationship.

The same opportunity does not result from the event of birth, as a matter of biological inevitability, in the case of the unwed father. Given the 9-month interval between conception and birth, it is not always certain that a father will know that a child was conceived, nor is it always clear that even the mother will be sure of the father's identity. This fact takes on particular significance in the case of a child born overseas and out of wedlock. One concern in this context has always been with young people, men for the most part, who are on duty with the Armed Forces in foreign countries. See Department of Defense, Selected Manpower Statistics 48, 74 (1999) (reporting that in 1969, the year in which Nguyen was born, there were 3,458,072 active duty military personnel, 39,506 of whom were female); Department of Defense, Selected Manpower Statistics 29 (1970) (noting that 1,041,094 military personnel were stationed in foreign countries in 1969); Department of Defense, Selected Manpower Statistics 49, 76 (1999) (reporting that in 1999 there were 1,385,703 active duty military personnel, 200,287 of whom were female); id. at 33 (noting that 252,763 military personnel were stationed in foreign countries in 1999).

When we turn to the conditions which prevail today, we find that the passage of time has produced additional and even more substantial grounds to justify the statutory distinction. The ease of travel and the willingness of Americans to visit foreign countries have resulted in numbers of trips abroad that must be of real concern when we contemplate the prospect of accepting petitioners' argument, which would mandate, contrary to Congress' wishes, citizenship by male parentage subject to no condition save the father's previous length of residence in this country. In 1999 alone, Americans made almost 25 million trips abroad, excluding trips to Canada and Mexico. See U.S. Dept. of Commerce, 1999 Profile of U.S. Travelers to Overseas Destinations 1 (Oct. 2000). Visits to Canada and Mexico add to this figure almost 34 million additional visits. See U.S. Dept. of Commerce, U.S. Resident Travel to Overseas Countries, Historical Visitation 1989-1999, p. 1 (Oct. 2000). And the average American overseas traveler spent 15.1 nights out of the United States in 1999. 1999 Profile of U.S. Travelers to Overseas Destinations, supra, at 4.

Principles of equal protection do not require Congress to ignore this reality. To the contrary, these facts demonstrate the critical importance of the Government's interest in ensuring some opportunity for a tie between citizen father and foreign born child which is a reasonable substitute for the opportunity manifest between mother and child at the time of birth. Indeed, especially in light of the number of Americans who take short sojourns abroad, the prospect that a father might not even know of the conception is a realistic possibility. See Miller, supra, at 439 (opinion of STEVENS, J.). Even if a father knows of the fact of conception, moreover, it does not follow that he will be present at the birth of the child. Thus, unlike the case of the mother, there is no assurance that the father and his biological child will ever meet. Without an initial point of contact with the child by a father who knows the child is his own, there is no opportunity for father and child to begin a relationship. Section 1409 takes the unremarkable step of ensuring that such an opportunity, inherent in the event of birth as to the mother-child relationship, exists between father and child before citizenship is conferred upon the latter.

The importance of the governmental interest at issue here is too profound to be satisfied merely by conducting a DNA test. The fact of paternity can be established even without the father's knowledge, not to say his presence. Paternity can be established by taking DNA samples even from a few strands of hair, years after the birth. See Federal Judicial Center, Reference Manual on Scientific Evidence 497 (2d ed. 2000). Yet scientific proof of biological paternity does nothing, by itself, to ensure contact between father and child during the child's minority.

Congress is well within its authority in refusing, absent proof of at least the opportunity for the development of a relationship between citizen parent and child, to commit this country to embracing a child as a citizen entitled as of birth to the full protection of the United States, to the absolute right to enter its borders, and to full participation in the political process. If citizenship is to be conferred by the unwitting means petitioners urge, so that its acquisition abroad bears little relation to the realities of the child's own ties and allegiances, it is for Congress, not this Court, to make that determination. Congress has not taken that path but has instead chosen, by means of § 1409, to ensure in the case of father and child the opportunity for a relationship to develop, an opportunity which the event of birth itself provides for the mother and child. It should be unobjectionable for Congress to require some evidence of a minimal opportunity for the development of a relationship with the child in terms the male can fulfill.

Petitioners and their amici argue in addition that, rather than fulfilling an important governmental interest, § 1409 merely embodies a gender-based stereotype. Although the above discussion should illustrate that, contrary to petitioners' assertions, § 1409 addresses an undeniable difference in the circumstance of the parents at the time a child is born, it should be noted, furthermore, that the difference does not result from some stereotype, defined as a frame of mind resulting from irrational or uncritical analysis. There is nothing irrational or improper in the recognition that at the moment of birth -- a critical event in the statutory scheme and in the whole tradition of citizenship law -- the mother's knowledge of the child and the fact of parenthood have been established in a way not guaranteed in the case of the unwed father. This is not a stereotype. See Virginia, 518 U.S. at 533 ("The heightened review standard our precedent establishes does not make sex a proscribed classification . . . . Physical differences between men and women . . . are enduring").

V

To fail to acknowledge even our most basic biological differences -- such as the fact that a mother must be present at birth but the father need not be -- risks making the guarantee of equal protection superficial, and so disserving it. Mechanistic classification of all our differences as stereotypes would operate to obscure those misconceptions and prejudices that are real. The distinction embodied in the statutory scheme here at issue is not marked by misconception and prejudice, nor does it show disrespect for either class. The difference between men and women in relation to the birth process is a real one, and the principle of equal protection does not forbid Congress to address the problem at hand in a manner specific to each gender.

The judgment of the Court of Appeals is Affirmed.

DISSENT: JUSTICE O'CONNOR, with whom JUSTICE SOUTER, JUSTICE GINSBURG, and JUSTICE BREYER join, dissenting.

I

… Sex-based statutes, even when accurately reflecting the way most men or women behave, deny individuals opportunity. Such generalizations must be viewed not in isolation, but in the context of our Nation's "'long and unfortunate history of sex discrimination.'" J. E. B. v. Alabama ex rel. T. B., 511 U.S. 127, 136, 128 L. Ed. 2d 89, 114 S. Ct. 1419 (1994) (quoting Frontiero v. Richardson, 411 U.S. 677, 684, 36 L. Ed. 2d 583, 93 S. Ct. 1764 (1973) (plurality opinion)). Sex-based generalizations both reflect and reinforce "fixed notions concerning the roles and abilities of males and females." Mississippi Univ. for Women v. Hogan, 458 U.S. 718, 725, 73 L. Ed. 2d 1090, 102 S. Ct. 3331 (1982).

A

According to the Court, "the first governmental interest to be served is the importance of assuring that a biological parent-child relationship exists." Ante, at 7. The majority does not elaborate on the importance of this interest, which presumably lies in preventing fraudulent conveyances of citizenship.

B

The Court states that "the second important governmental interest furthered in a substantial manner by § 1409(a)(4) is the determination to ensure that the child and the citizen parent have some demonstrated opportunity or potential to develop not just a relationship that is recognized, as a formal matter, by the law, but one that consists of the real, everyday ties that provide a connection between child and citizen parent and, in turn, the United States." Ante, at 9-10. 

Assuming, as the majority does, that Congress was actually concerned about ensuring a "demonstrated opportunity" for a relationship, it is questionable whether such an opportunity qualifies as an "important" governmental interest apart from the existence of an actual relationship. By focusing on "opportunity" rather than reality, the majority presumably improves the chances of a sufficient means-end fit. But in doing so, it dilutes significantly the weight of the interest. It is difficult to see how, in this citizenship-conferral context, anyone profits from a "demonstrated opportunity" for a relationship in the absence of the fruition of an actual tie. Children who have an "opportunity" for such a tie with a parent, of course, may never develop an actual relationship with that parent. See Miller, 523 U.S. at 440 (opinion of STEVENS, J.). If a child grows up in a foreign country without any postbirth contact with the citizen parent, then the child's never-realized  "opportunity" for a relationship with the citizen seems singularly irrelevant to the appropriateness of granting citizenship to that child. Likewise, where there is an actual relationship, it is the actual relationship that does all the work in rendering appropriate a grant of citizenship, regardless of when and how the opportunity for that relationship arose.

Accepting for the moment the majority's focus on "opportunity," the attempt to justify § 1409(a)(4) in these terms is still deficient. Even if it is important "to require that an opportunity for a parent-child relationship occur during the formative years of the child's minority," ante, at 13, it is difficult to see how the requirement that proof of such opportunity be obtained before the child turns 18 substantially furthers the asserted interest. As the facts of this case demonstrate, ante, at 2, it is entirely possible that a father and child will have the opportunity to develop a relationship and in fact will develop a relationship without obtaining the proof of the opportunity during the child's minority. After his parents' relationship had ended, petitioner Nguyen lived with the family of his father's new girlfriend. In 1975, before his sixth birthday, Nguyen came to the United States, where he was reared by his father, petitioner Boulais. In 1997, a DNA test showed a 99.98% probability of paternity, and, in 1998, Boulais obtained an order of parentage from a Texas court.

Indeed, the idea that a mother's presence at birth supplies adequate assurance of an opportunity to develop a relationship while a father's presence at birth does not would appear to rest only on an overbroad sex-based generalization. A mother may not have an opportunity for a relationship if the child is removed from his or her mother on account of alleged abuse or neglect, or if the child and mother are separated by tragedy, such as disaster or war, of the sort apparently present in this case. There is no reason, other than stereotype, to say that fathers who are present at birth lack an opportunity for a relationship on similar terms. The "physical differences between men and women," Virginia, 518 U.S. at 533, therefore do not justify § 1409(a)(4)'s discrimination.

The question that then remains is the sufficiency of the fit between § 1409(a)(4)'s discriminatory means and the goal of "establishing . . . a real, practical relationship of considerable substance." Ante, at 15. If Congress wishes to advance this end, it could easily do so by employing a sex-neutral classification that is a far "more germane basis of classification" than sex, Craig, 429 U.S. at 198. For example, Congress could require some degree of regular contact between the child and the citizen parent over a period of time. See Miller, 523 U.S. at 470 (GINSBURG, J., dissenting).

The claim that § 1409(a)(4) substantially relates to the achievement of the goal of a "real, practical relationship" thus finds support not in biological differences but instead in a stereotype -- i.e., "the generalization that mothers are significantly more likely than fathers . . . to develop caring relationships with their children." Miller, supra, at 482-483 (BREYER, J., dissenting). Such a claim relies on "the very stereotype the law condemns," J. E. B., 511 U.S. at 138 (internal quotation marks omitted), "lends credibility" to the generalization, Mississippi Univ. for Women, 458 U.S. at 730, and helps to convert that "assumption" into "a self-fulfilling prophecy," ibid. See also J. E. B., supra, at 140 ("When state actors exercise peremptory challenges in reliance on gender stereotypes, they ratify and reinforce prejudicial views of the relative abilities of men and women"). Indeed, contrary to this stereotype, Boulais has reared Nguyen, while Nguyen apparently has lacked a relationship with his mother.

The majority apparently tries to avoid reliance on this stereotype by characterizing the governmental interest as a "demonstrated opportunity" for a relationship and attempting to close the gap between opportunity and reality with a dubious claim about what is "almost axiomatic." But the fact that one route is wisely forgone does not mean that the other is plausibly taken. The inescapable conclusion instead is that § 1409(a)(4) lacks an exceedingly persuasive justification.

C

The Court has also failed even to acknowledge the "volumes of history" to which "today's skeptical scrutiny of official action denying rights or opportunities based on sex responds." Id. at 531. The history of sex discrimination in laws governing the transmission of citizenship and with respect to parental responsibilities for children born out of wedlock counsels at least some circumspection in discerning legislative purposes in this context. See generally Miller, supra, at 460-468 (GINSBURG, J., dissenting).

Section 1409 was first enacted as § 205 of the Nationality Act of 1940, 54 Stat. 1139-1140. The 1940 Act had been proposed by the President, forwarding a report by a specially convened Committee of Advisors, including the Attorney General. The Committee explained to Congress the rationale for § 205, whose sex-based classification remains in effect today:

"The Department of State has, at least since 1912, uniformly held that an illegitimate child born abroad of an American mother acquires at birth the nationality of the mother, in the absence of legitimation or adjudication establishing the paternity of the child. This ruling is based . . . on the ground that the mother in such case stands in the place of the father. . . . Under American law the mother has a right to custody and control of such child as against the putative father, and is bound to maintain it as its natural guardian. This rule seems to be in accord with the old Roman law and with the laws of Spain and France." To Revise and Codify the Nationality Laws of the United States, Hearings on H. R. 6127 before the House Committee on Immigration and Naturalization, 76th Cong., 1st Sess., 431 (1945) (reprinting Message from the President, Nationality Laws of the United States (1938)) (emphasis added and internal quotation marks and citations omitted).

Section 1409(a)(4) is thus paradigmatic of a historic regime that left women with responsibility, and freed men from responsibility, for nonmarital children. Under this law, as one advocate explained to Congress in a 1932 plea for a sex-neutral citizenship law, "when it comes to the illegitimate child, which is a great burden, then the mother is the only recognized parent, and the father is put safely in the background." Naturalization and Citizenship Status of Certain Children of Mothers Who Are Citizens of the United States, Hearing on H. R. 5489 before the House Committee on Immigration and Naturalization, 72nd Cong., 1st Sess., 3 (testimony of Burnita Shelton Matthews); see also id. at 5 (citizenship law "permits [the father] to escape the burdens incident to illegitimate parenthood"). Unlike § 1409(a)(4), our States' child custody and support laws no longer assume that mothers alone are "bound" to serve as "natural guardians" of nonmarital children. See, e.g., Ariz. Rev. Stat. Ann. § 25-501 (1999) (equal duties of support); cf. Cal. Civ. Code Ann. § 4600 (West 1972) (abolishing "tender years" doctrine). The majority, however, rather than confronting the stereotypical notion that mothers must care for these children and fathers may ignore them, quietly condones the "very stereotype the law condemns," J. E. B., 511 U.S. at 138 (internal quotation marks omitted).