Court opinion, as written by Chief Justice Marshall:
Marriage is a vital social institution. The exclusive commitment of two individuals to each other nurtures love and mutual support; it brings stability to our society. For those who choose to marry, and for their children, marriage provides an abundance of legal, financial, and social benefits. In return it imposes weighty legal, financial, and social obligations. The question before us is whether, consistent with the Massachusetts Constitution, the Commonwealth may deny the protections, benefits, and obligations conferred by civil marriage to two individuals of the same sex who wish to marry. We conclude that it may not. The Massachusetts Constitution affirms the dignity and equality of all individuals. It forbids the creation of second-class citizens. In reaching our conclusion we have given full deference to the arguments made by the Commonwealth. But it has failed to identify any constitutionally adequate reason for denying civil marriage to same-sex couples.
We are mindful that our decision marks a change in the history of our marriage law. Many people hold deep-seated religious, moral, and ethical convictions that marriage should be limited to the union of one man and one woman, and that homosexual conduct is immoral. Many hold equally strong religious, moral, and ethical convictions that same-sex couples are entitled to be married, and that homosexual persons should be treated no differently than their heterosexual neighbors. Neither view answers the question before us. Our concern is with the Massachusetts Constitution as a charter of governance for every person properly within its reach. "Our obligation is to define the liberty of all, not to mandate our own moral code." Lawrence v. Texas, 123 S. Ct. 2472, 2480 (2003) (Lawrence), quoting Planned Parenthood of Southeastern Pa. v. Casey, 505 U.S. 833, 850 (1992).
Whether the Commonwealth may use its formidable regulatory authority to bar same-sex couples from civil marriage is a question not previously addressed by a Massachusetts appellate court. It is a question the United States Supreme Court left open as a matter of Federal law in Lawrence, supra at 2484, where it was not an issue. There, the Court affirmed that the core concept of common human dignity protected by the Fourteenth Amendment to the United States Constitution precludes government intrusion into the deeply personal realms of consensual adult expressions of intimacy and one's choice of an intimate partner. The Court also reaffirmed the central role that decisions whether to marry or have children bear in shaping one's identity. Id. at 2481. The Massachusetts Constitution is, if anything, more protective of individual liberty and equality than the Federal Constitution; it may demand broader protection for fundamental rights; and it is less tolerant of government intrusion into the protected spheres of private life.
Barred access to the protections, benefits, and obligations of civil marriage, a person who enters into an intimate, exclusive union with another of the same sex is arbitrarily deprived of membership in one of our community's most rewarding and cherished institutions. That exclusion is incompatible with the constitutional principles of respect for individual autonomy and equality under law.
We construe civil marriage to mean the voluntary union of two persons as spouses, to the exclusion of all others. This reformulation redresses the plaintiffs' constitutional injury and furthers the aim of marriage to promote stable, exclusive relationships. It advances the two legitimate State interests the department has identified: providing a stable setting for child rearing and conserving State resources. It leaves intact the Legislature's broad discretion to regulate marriage. See Commonwealth v. Stowell, 389 Mass. 171, 175 (1983).
In their complaint the plaintiffs request only a declaration that their exclusion and the exclusion of other qualified same-sex couples from access to civil marriage violates Massachusetts law. We declare that barring an individual from the protections, benefits, and obligations of civil marriage solely because that person would marry a person of the same sex violates the Massachusetts Constitution. We vacate the summary judgment for the department. We remand this case to the Superior Court for entry of judgment consistent with this opinion. Entry of judgment shall be stayed for 180 days to permit the Legislature to take such action as it may deem appropriate in light of this opinion. See, e.g., Michaud v. Sheriff of Essex County, 390 Mass. 523, 535-536 (1983).
- - - - - - - - - - - -
Justice Spina (dissenting, with whom Justices Sosman and Cordy join):
What is at stake in this case is not the unequal treatment of individuals or whether individual rights have been impermissibly burdened, but the power of the Legislature to effectuate social change without interference from the courts, pursuant to art. 30 of the Massachusetts Declaration of Rights. The power to regulate marriage lies with the Legislature, not with the judiciary. See Commonwealth v. Stowell, 389 Mass. 171, 175 (1983). Today, the court has transformed its role as protector of individual rights into the role of creator of rights, and I respectfully dissent.
The court has extruded a new right from principles of substantive due process, and in doing so it has distorted the meaning and purpose of due process. The purpose of substantive due process is to protect existing rights, not to create new rights. Its aim is to thwart government intrusion, not invite it. The court asserts that the Massachusetts Declaration of Rights serves to guard against government intrusion into each individual's sphere of privacy. Ante at . Similarly, the Supreme Court has called for increased due process protection when individual privacy and intimacy are threatened by unnecessary government imposition. See, e.g., Lawrence v. Texas, 123 S. Ct. 2472 (2003) (private nature of sexual behavior implicates increased due process protection); Eisenstadt v. Baird, 405 U.S. 438 (1972) (privacy protection extended to procreation decisions within nonmarital context); Griswold v. Connecticut, 381 U.S. 479 (1965) (due process invoked because of intimate nature of procreation decisions). These cases, along with the Moe case, focus on the threat to privacy when government seeks to regulate the most intimate activity behind bedroom doors. The statute in question does not seek to regulate intimate activity within an intimate relationship, but merely gives formal recognition to a particular marriage. The State has respected the private lives of the plaintiffs, and has done nothing to intrude in the relationships that each of the plaintiff couples enjoy. Cf. Lawrence v. Texas, supra at 2484 (case "does not involve whether the government must give formal recognition to any relationship that homosexual persons seek to enter"). Ironically, by extending the marriage laws to same-sex couples the court has turned substantive due process on its head and used it to interject government into the plaintiffs lives.
Justice Sosman (dissenting, with whom Justices Spina and Cordy join):
In applying the rational basis test to any challenged statutory scheme, the issue is not whether the Legislature's rationale behind that scheme is persuasive to us, but only whether it satisfies a minimal threshold of rationality. Today, rather than apply that test, the court announces that, because it is persuaded that there are no differences between same-sex and opposite-sex couples, the Legislature has no rational basis for treating them differently with respect to the granting of marriage licenses. Reduced to its essence, the court's opinion concludes that, because same-sex couples are now raising children, and withholding the benefits of civil marriage from their union makes it harder for them to raise those children, the State must therefore provide the benefits of civil marriage to same-sex couples just as it does to opposite-sex couples. Of course, many people are raising children outside the confines of traditional marriage, and, by definition, those children are being deprived of the various benefits that would flow if they were being raised in a household with married parents. That does not mean that the Legislature must accord the full benefits of marital status on every household raising children. Rather, the Legislature need only have some rational basis for concluding that, at present, those alternate family structures have not yet been conclusively shown to be the equivalent of the marital family structure that has established itself as a successful one over a period of centuries. People are of course at liberty to raise their children in various family structures, as long as they are not literally harming their children by doing so. See Blixt v. Blixt, 437 Mass. 649, 668-670 (2002) (Sosman, J., dissenting), cert. denied, 537 U.S. 1189 (2003). That does not mean that the State is required to provide identical forms of encouragement, endorsement, and support to all of the infinite variety of household structures that a free society permits.
Based on our own philosophy of child rearing, and on our observations of the children being raised by same-sex couples to whom we are personally close, we may be of the view that what matters to children is not the gender, or sexual orientation, or even the number of the adults who raise them, but rather whether those adults provide the children with a nurturing, stable, safe, consistent, and supportive environment in which to mature...
It is not, however, our assessment that matters. Conspicuously absent from the court's opinion today is any acknowledgment that the attempts at scientific study of the ramifications of raising children in same-sex couple households are themselves in their infancy and have so far produced inconclusive and conflicting results...Gay and lesbian couples living together openly, and official recognition of them as their children's sole parents, comprise a very recent phenomenon, and the recency of that phenomenon has not yet permitted any study of how those children fare as adults and at best minimal study of how they fare during their adolescent years. The Legislature can rationally view the state of the scientific evidence as unsettled on the critical question it now faces: Are families headed by same-sex parents equally successful in rearing children from infancy to adulthood as families headed by parents of opposite sexes? Our belief that children raised by same-sex couples should fare the same as children raised in traditional families is just that: a passionately held but utterly untested belief. The Legislature is not required to share that belief but may, as the creator of the institution of civil marriage, wish to see the proof before making a fundamental alteration to that institution.
More importantly, it is not our confidence in the lack of adverse consequences that is at issue, or even whether that confidence is justifiable. The issue is whether it is rational to reserve judgment on whether this change can be made at this time without damaging the institution of marriage or adversely affecting the critical role it has played in our society. Absent consensus on the issue (which obviously does not exist), or unanimity amongst scientists studying the issue (which also does not exist), or a more prolonged period of observation of this new family structure (which has not yet been possible), it is rational for the Legislature to postpone any redefinition of marriage that would include same-sex couples until such time as it is certain that that redefinition will not have unintended and undesirable social consequences. Through the political process, the people may decide when the benefits of extending civil marriage to same-sex couples have been shown to outweigh whatever risks -- be they palpable or ephemeral -- are involved. However minimal the risks of that redefinition of marriage may seem to us from our vantage point, it is not up to us to decide what risks society must run, and it is inappropriate for us to abrogate that power to ourselves merely because we are confident that "it is the right thing to do." Ante at (Greaney, J., concurring).
- - - - - - - - - - - -
 For American appellate courts that have recently addressed this issue, see Standhardt v. Superior Court, 77 P.3d 451 (Ariz. Ct. App. 2003); Dean v. District of Columbia, 653 A.2d 307 (D.C. 1995); Baehr v. Lewin, 74 Haw. 530 (1993); Baker v. State, 170 Vt. 194, 242 (1999). Earlier cases include Adams v. Howerton, 486 F. Supp. 1119 (C.D. Cal. 1980), aff'd, 673 F.2d 1036 (9th Cir.), cert. denied, 458 U.S. 1111 (1982); Jones v. Hallahan, 501 S.W.2d 588 (Ky. Ct. App. 1973); Baker v. Nelson, 291 Minn. 310 (1971), appeal dismissed, 409 U.S. 810 (1972); Singer v. Hara, 11 Wash. App. 247 (1974). See also Halpern v. Toronto (City), 172 O.A.C. 276 (2003); Egale Canada, Inc. v. Canada (Attorney Gen.), 13 B.C.L.R. (4th) 1 (2003).
 Article 30 of the Massachusetts Declaration of Rights provides that "the judicial [department] shall never exercise the legislative and executive powers ... to the end it may be a government of laws and not of men."
 The one difference that the court acknowledges -- that sexual relations between persons of the same sex does not result in pregnancy and childbirth -- it immediately brushes aside on the theory that civil marriage somehow has nothing to do with begetting children ... For the reasons explained in detail in Justice Cordy's dissent, in which I join, the reasons justifying the civil marriage laws are inextricably linked to the fact that human sexual intercourse between a man and a woman frequently results in pregnancy and childbirth. Indeed, as Justice Cordy outlines, that fact lies at the core of why society fashioned the institution of marriage in the first place. Post at (Cordy, J., dissenting).