The Defense of Marriage Act, the 1996 law that defines "marriage" and "spouse" under federal law as only pertaining to marriages between one man and one woman, is unconstitutional, the federal appeals court out of New York ruled on Thursday.

The 2-1 opinion of the Second Circuit Court of Appeals in Edith Windsor's case came just three weeks after the three-judge panel heard oral arguments from the lawyers in the case. It is the second appeals court to hold the law unconstitutional, and the Supreme Court has several requests pending to resolve the constitutionality of the law.

The opinion — authored by the conservative chief judge of the Second Circuit, Dennis Jacobs — is another blow to the House Republican leadership, which has been defending the law since the Obama administration determined that the law is unconstitutional in February 2011.

Beyond striking down the law itself, the most significant development in today's ruling is that the Second Circuit held that laws that classify people based on sexual orientation, like DOMA, should be subjected to a heightened form of scrutiny when courts examine the government's claimed reasons for such laws. The holding that "intermediate scrutiny" applies makes the Second Circuit the first federal appeals court to do so. The First Circuit did not apply heightened scrutiny in its earlier decision striking down DOMA.

The Second Circuit, however, held:

In this case, all four factors justify heightened scrutiny: A) homosexuals as a group have historically endured persecution and discrimination; B) homosexuality has no relation to aptitude or ability to contribute to society; C) homosexuals are a discernible group with non-obvious distinguishing characteristics, especially in the subset of those who enter same-sex marriages; and D) the class remains a politically weakened minority.

Chief Judge Jacobs, appointed to the bench by President George H.W. Bush, was joined in his opinion by Judge Christopher Droney, an Obama appointee. The opinion, at points, is almost strident in its support for its conclusions. As to the history of discrimination, for example, he wrote:

It is easy to conclude that homosexuals have suffered a history of discrimination. Windsor and several amici labor to establish and document this history, but we think it is not much in debate.

Referring to the House Republican leadership, which is defending the law in court because it holds a 3-2 majority on the House's Bipartisan Legal Advisory Group, Jacobs wrote:

BLAG argues that, unlike protected classes, homosexuals have not "suffered discrimination for longer than history has been recorded." But whether such discrimination existed in Babylon is neither here nor there. BLAG concedes that homosexuals have endured discrimination in this country since at least the 1920s. Ninety years of discrimination is entirely sufficient to document a "history of discrimination."

As to political powerlessness, one of the more hotly debated point at oral arguments, the majority opinion is again direct:

The question is not whether homosexuals have achieved political successes over the years; they clearly have. The question is whether they have the strength to politically protect themselves from wrongful discrimination.

When discussing successes that lesbian, gay and bisexual people have had in getting elected to public office, however, Jacobs also provided some nuanced analysis (although not expressed in the language used by LGBT advocates):

It is difficult to say whether homosexuals are "under-represented" in positions of power and authority without knowing their number relative to the heterosexual population. But it is safe to say that the seemingly small number of acknowledged homosexuals so situated is attributable either to a hostility that excludes them or to a hostility that keeps their sexual preference private—which, for our purposes, amounts to much the same thing.

Once the court determined that intermediate scrutiny applied — which requires the government to show that the law is "substantially related to an important government interest" — the court quickly dismissed the reasons given by the lawyer for the House Republican leaders, Paul Clement. It noted, even, that Clement "all but conceded that these reasons for enacting DOMA may not withstand intermediate scrutiny."

Of the reason primarily advanced by Clement, that Congress had the right to pass a law aimed at maintaining "uniformity" on marriage, the court held:

Because DOMA is an unprecedented breach of longstanding deference to federalism that singles out same-sex marriage as the only inconsistency (among many) in state law that requires a federal rule to achieve uniformity, the rationale premised on uniformity is not an exceedingly persuasive justification for DOMA.

After dismissing the other reasons advanced by the House Republican leaders, the court concluded: "[W]e hold that Section 3 of DOMA violates equal protection and is therefore unconstitutional."

The dissenting opinion came from Judge Chester Straub, a Clinton appointee, who argued that a 1972 Supreme Court decision in which the court found that a same-sex couple denied a marriage license in Minnesota did not raise a "substantial federal question" in their constitutional challenge bound him in this case because the Supreme Court had never overruled the case.

Similarly, he argued that the court was wrong to apply heightened scrutiny because the Supreme Court has not done so. Under the lowest form of scrutiny, called rational basis, Straub wrote that the law should be found to be constitutional because "DOMA centers on legitimate state interests that go beyond mere moral disapproval of an excluded group."

Both the American Civil Liberties Union and their outside counsel, Paul Weiss's Roberta Kaplan, have asked the Supreme Court to review this case, as has the Department of Justice.