In his legal brief supporting Mrs. Windsor, Schneiderman asserts that the Defense of Marriage Act is unacceptable because,
Schneiderman not only argues that DOMA should fail based upon sexual orientation and gender discrimination, but also because it violates one of the key principles of Federalism contained in the 10th Amendment of the U.S. Constitution - that is, that the powers not delegated to the federal government, in this case marriage, should be, and have historically been, left to the individual states. This 10th Amendment rational was also one of the key reasons that Massachusetts judge Joseph Tauro deemed DOMA unconstitutional.By refusing to recognize for federal purposes marriages that are valid under state law, DOMA intrudes on matters historically within the control of the States, and undermines and denigrates New York’s law designed to ensure equality of same-sex and different-sex married couples. Thus DOMA threatens basic principles of federalism. Moreover, it classifies and determines access to rights, benefits, and protections based on sexual orientation, and also based on sex.
Additionally, Schneiderman asserts in his brief that DOMA does not allow the State of New York to fully realize equality in its marriage laws saying,
Because New York has consistently expressed and implemented its commitment to equal treatment for same-sex couples, New York has a strong interest in ensuring that the “protections, responsibilities, rights, obligations, and benefits,”, accorded to them under federal law by virtue of marriage are equal to those accorded to different-sex married couples. Without such equal treatment by the federal government, New York’s statutory commitment to marriage equality for all married couples will be substantially unrealized.