The U.S. Court of Appeals for the Second Circuit held that Section 3 of the Defense of Marriage Act ("DOMA") is unconstitutional because it violates equal protection.

In June, the US District Court for the Southern District of NY granted summary judgment to Edith Windsor, and held that the $363,053 Windsor was required to pay as executor of her wife's estate was improperly assessed because of the definition of marriage the IRS uses, as required under DOMA, which defines a "marriage" as a relationship between a man and a woman.

The court rejected the defendant's argument that under Baker v. Nelson, a Supreme Court case from 1971, Congress can prohibit same-sex marriage without violating the equal protection clause. The court ruled that Baker did not apply, because it was about whether a state could restrict same-sex marriage, so the holding did not apply to the issue of whether the federal government can define marriage constitutionally.

The court then determined that homosexuals compose a quasi suspect class that is subject to heightened scrutiny. The court rejected claims that DOMA protects "unique federal interests" such as maintaining a uniform definition of marriage, saving government resources by limited beneficiaries of government marital benefits, preserving a traditional understanding of marriage, and encouraging responsible procreation. The court rejected some of these arguments by noting that the decision of whether same sex couples can marry is left to the states, so DOMA – a federal law – is ineffective for most of these purposes.

Windsor is currently in front of the Supreme Court for certiorari.