President Barack Obama and his administration have called unconstitutional a part of the 1996 federal law that calls the government to define marriage to be a legal union between one man and one woman.

The administration will not defend Section 3 of the Defense of Marriage Act in two pending legal cases, U.S. Attorney General Eric Holder, said on Wednesday. 

Obama, with recommendation from Holder, has determined that the law was not constitutional and issued the order, Holder said.

The President will continue to enforce a section in the law within the departments under his control, however.

Holder made the declaration in letter to House Speaker John Boehner on Wednesday that the law will be enforced until Congress repeals the section of the law in question or when the courts make a verdict against the law's constitutionality.

After careful consideration, including review of a recommendation from me, the President of the United States has made the determination that Section 3 of the Defense of Marriage Act ..., as applied to same-sex couples who are legally married under state law, violates the equal protection component of the Fifth Amendment.

[T]he President and I have concluded that classifications based on sexual orientation warrant heightened scrutiny and that, as applied to same-sex couples legally married under state law, Section 3 of DOMA is unconstitutional, Holder said.

Holder's Letter

Holder's letter said the Supreme Court had yet to rule on the appropriate level of scrutiny for classifications based on sexual orientation. He outlined 4 criteria that should inform any judgment about whether heightened scrutiny applies.

In the first, Holder noted gay and lesbian people had been discriminated against by governmental and private entities.

In the second, he said that while sexual orientation carries no visible badge, a growing scientific consensus accepts that sexual orientation is a characteristic that is immutable.

It is undoubtedly unfair to require sexual orientation to be hidden from view to avoid discrimination, Holder said.

Thirdly, he said gays and lesbians as a group have limited political power due to the longstanding ban on gays and lesbians in the military, and the absence of federal protection for employment discrimination on the basis of sexual orientation show those in the group have limited political power and 'ability to attract the [favorable] attention of the lawmakers.'

Last year, President Barack Obama signed into law a bill repealing the Don't Ask, Don't Tell' Law in Congress.

Fourth, he said 'there is a growing acknowledgment that sexual orientation 'bears no relation to ability to perform or contribute to society,' he said, citing the pending repeal of the Don't Ask, don't Tell law that forbids individuals from divulging or being asked if they are homosexuals.

Recent evolutions in legislation ..., and in social science regarding sexual orientation all make clear that sexual orientation is not a characteristic that generally bears on legitimate policy objectives, he said.

Holder said DOMA's passage contains discussion and debate that undermines any defense under heightened scrutiny.

The record contains numerous expressions reflecting moral disapproval of gays and lesbians and their intimate and family relationships - precisely the kind of stereotype-based thinking and animus the Equal Protection Clause is designed to guard against, he said.