The discrimination embedded in the Defense of Marriage Act is precise yet sweeping. The 1996 statute defines marriage as the union of a man and a woman, and applies that definition to about 1,100 federal laws and programs. One of its many discriminatory results is that same-sex couples are prohibited from collecting many federal benefits available to other couples.

That now includes people legally married in nine states and the District of Columbia, plus 18,000 couples who were legally married in California before 2008 when Proposition 8 banned same-sex marriage there.

Solicitor General Donald Verrilli Jr., who is known for his reserve, was unhesitating before the Supreme Court on Wednesday when it heard the Defense of Marriage Act case: “I think it’s time for the court to recognize that this discrimination, excluding lawfully married gay and lesbian couples from federal benefits, cannot be reconciled with our fundamental commitment to equal treatment under law.” It appeared that a majority of the justices, including the likely swing vote, Justice Anthony Kennedy, had serious doubts as to whether the law served any legitimate purpose.

Justice Kennedy, however, seemed primarily interested in questioning the law for the wrong reasons, concerned that the Defense of Marriage Act interferes in the primary right of states to regulate marriage and its benefits. Only the four more liberal justices appeared to focus on the reality that what is at stake here is not federalism but fairness. States can regulate marriage but they cannot discriminate while doing so, and leaving gay and lesbian couples out of the equation violates the Constitution’s guarantee of equal protection just as much as banning interracial marriage.