ACLU:

A federal appeals court ruled today that the so-called “Defense of Marriage Act” (DOMA) unconstitutionally discriminates against married same-sex couples. In striking down DOMA, the court held that government discrimination against lesbians and gay men now is assumed to be unconstitutional and that DOMA’s defenders could not offer any good reason for treating married same-sex couples differently from all other married couples. This is the first federal appeals court decision to decide that government discrimination against gay people gets a more exacting level of judicial review, known as “heightened scrutiny.” The law had been challenged by Edith “Edie” Windsor, who sued the federal government for failing to recognize her marriage to her pa rtner Thea Spyer, after Spyer’s death in 2009. Windsor and Spyer, who were a couple for 44 years, were married in Canada in 2007, and were considered married by their home state of New York.

Full text of the decision here—and it's worth a read. The justices demolish every argument the haters make against recognizing same-sex marriage, from homosexuals being able to change to homosexuality being a mutable characteristic to homosexuals being too political powerful to rely on the courts for protection. Go read it.

UPDATE: The judge who wrote the decision, reports Think Progress, is a severe conservative.