Electronic Arts, Microsoft, and Zynga are among many companies who have signed an amicus brief that opposes the United States' Defense of Marriage Act.
The Act, which defines marriage as the legal union between one man and one woman, is one of the largest obstacles against gay marriage in the States; one President Barack Obama promised to repeal.
The brief states that the Defense of Marriage act is discriminatory, hurts morale, and creates uncomfortable tax issues within organisations.
The parties in the brief, which also include Viacom, Starbucks, and the cities of New York and San Francisco among others, are urging the Ninth Circuit Court of Appeals to find portions of DOMA unconstitutional.
The brief was filed in the case of Karen Golinski v. the US Office of Personnel Management, which is examining the validity of DOMA.
EA has been particularly supportive of LGBT rights, participating in the San Francisco and Seattle Pride events this year as well as the "It Gets Better" Internet campaign.