Justice Kennedy lays out the majority's opinion in four concise points:
Four principles and traditions demonstrate that the reasons marriage is fundamental under the Constitution apply with equal force to same-sex couples. The first premise of this Court’s relevant precedents is that the right to personal choice regarding marriage is inherent in the concept of individual autonomy. This abiding connection between marriage and liberty is why Loving invalidated interracial marriage bans under the Due Process Clause. See 388 U. S., at 12. Decisions about marriage are among the most intimate that an individual can make. See Lawrence, supra, at 574. This is true for all persons, whatever their sexual orientation.
A second principle in this Court’s jurisprudence is that the right to marry is fundamental because it supports a two-person union unlike any other in its importance to the committed individuals. The intimate association protected by this right was central to Griswold v. Connecticut, which held the Constitution protects the right of married couples to use contraception, 381 U. S., at 485, and was acknowledged in Turner, supra, at 95. Same-sex couples have the same right as opposite-sex couples to enjoy intimate association, a right extending beyond mere freedom from laws making same-sex intimacy a criminal offense. See Lawrence, supra, at 567.
A third basis for protecting the right to marry is that it safeguards children and families and thus draws meaning from related rights of childrearing, procreation, and education. See, e.g., Pierce v. Society of Sisters, 268 U. S. 510. Without the recognition, stability, and predictability marriage offers, children suffer the stigma of knowing their families are somehow lesser. They also suffer the significant material costs of being raised by unmarried parents, relegated to a more difficult and uncertain family life. The marriage laws at issue thus harm and humiliate the children of same-sex couples. See Windsor, supra, at _
. This does not mean that the right to marry is less meaningful for those who do not or cannot have children. Precedent protects the right of a married couple not to procreate, so the right to marry cannot be conditioned on the capacity or commitment to procreate.
Finally, this Court’s cases and the Nation’s traditions make clear that marriage is a keystone of the Nation’s social order. See Maynard v. Hill, 125 U. S. 190, 211. States have contributed to the fundamental character of marriage by placing it at the center of many facets of the legal and social order. There is no difference between same- and opposite-sex couples with respect to this principle, yet same-sex couples are denied the constellation of benefits that the States have linked to marriage and are consigned to an instability many opposite-sex couples would find intolerable. It is demeaning to lock same-sex couples out of a central institution of the Nation’s society, for they too may aspire to the transcendent purposes of marriage. The limitation of marriage to opposite-sex couples may long have seemed natural and just, but its inconsistency with the central meaning of the fundamental right to marry is now manifest. Pp. 12–18.http://www.supremecourt.gov/opinions/14pdf/14-556_3204.pdf