Attorney general’s office files amicus brief urging Supreme Court to strike down gay marriage bans

By Peter Schworm, Globe Staff

Martha Coakley, the state’s attorney general, filed an amicus brief Thursday urging the US Supreme Court to strike down California’s ban on same-sex marriage, saying Proposition 8 “is in clear conflict with our Constitution.”

“Proposition 8’s exclusion of same-sex couples from marriage is unconstitutional,” Coakley writes in the 31-page brief. “Denying gays and lesbians the opportunity to wed the partner of their choosing does not advance any legitimate governmental interest.”

Thirteen other states, including New York, Illinois, and Maryland, join Massachusetts in the brief, which asserts that the California law violates equal protection rights. Some of the states, such as New Mexico and Illinois, have not legalized gay marriage.

“Proposition 8 codifies the second-class status — for its own sake — of gays, lesbians, and their families,” the brief states. “Under any standard of Equal Protection analysis, it cannot survive review.”

Next month, the Supreme Court will hear arguments about the constitutionality of the ban, and will also hear a challenge to the federal Defense of Marriage Act, which defines marriage solely as a union between a man and a woman.

California voters approved Proposition 8 in 2008 after the state’s Supreme Court granted same-sex couples the right to marry. Last February, a federal appeals court declared the measure unconstitutional, spurring supporters of the law to seek Supreme Court review.

On Wednesday, the attorney general in California urged the high court to rule against the ban, saying its sole effect was to “strip loving relationships of validation and dignity under law.”

On Friday, Coakley’s office, along with the New York attorney general, will submit a brief urging the high court to strike down the federal law, known as DOMA.

“The Defense of Marriage Act represents an unprecedented intrusion into an area of law that has always been controlled by the states,” Coakley said in a statement released by her office. “This discriminatory and unconstitutional law harms thousands of families in Massachusetts and takes away our state’s right to extend marriage equality to all couples. We urge the Supreme Court to take the important final step toward ensuring equality for all.”

In the brief filed today, Coakley writes the societal benefits of marriage should be available to all.

“Since the founding, states have sanctioned marriages to support families, strengthen communities, and facilitate governance,” the brief argued. “Because same-sex couples avail themselves of the benefits and abide by the obligations of marriage in precisely the same manner as different-sex couples, the states’ interests in marriage are furthered by allowing same-sex couples to marry.”

The ban also deprives children of same-sex couples of the benefits of being raised “in a secure, protected family unit with two married parents,” Coakley wrote.

“As a result, Proposition 8 impedes the very interest in children that petitioners purport to serve.”

In 2009, Massachusetts became the first and only state to challenge DOMA, saying Congress intruded into a matter that should be left to the states. The following year, a federal district court judge in Boston struck down the law as unconstitutional, a ruling that was upheld on appeal last year.

That case was appealed to the Supreme Court, but the court decided to consider a different DOMA challenge, stemming from a case in New York.