animus towards gay and lesbian people , '' the state wrote in the lawsuit , which was filed Wednesday in federal court . Massachusetts , the first state to legalize gay marriage , said that about 16,000 same-sex couples have been married there since 2004 , when it began issuing marriage licenses . Since that time , the lawsuit said , `` the security and stability of families has been strengthened in important ways throughout the state . '' The state is challenging Section 3 of the law , which defines marriage as '' a legal union between one man and one woman as husband and wife '' and a spouse as `` a person of the opposite sex who is a husband or a wife . '' Before the act , the lawsuit argues , defining marital status was the prerogative of the states . The law `` eviscerated more than 200 years of federal government deference to the states with respect to defining marriage , '' it said . The lawsuit also argues that the law forces Massachusetts to treat same-sex married couples differently from heterosexual married couples , particularly through determining who qualifies for the state 's
-LRB- CNN -RRB- -- Massachusetts sued the U.S. government on Wednesday , challenging the constitutionality of a federal law that defines marriage as the union of a man and a woman . The state of Massachusetts says the Defense of Marriage Act denies same-sex couples essential rights . `` We 're taking this action today because , first , we believe that -LSB- the Defense of Marriage Act -RSB- directly interferes with Massachusetts ' long-standing sovereign authority to define and regulate the marital status of its residents , '' Attorney General Martha Coakley said Wednesday afternoon . `` Massachusetts has a single category of married persons , and we view all married persons equally and identically , '' she said . `` DOMA divides that category into two distinct and unequal classes of marriage . '' The lawsuit argues that the act , which became law in 1996 , denies same-sex couples essential rights and protections , including federal income tax credits , employment and retirement benefits , health insurance coverage and Social Security payments . `` In enacting DOMA , Congress overstepped its authority , undermined states ' efforts to recognize marriages between same-sex couples , and codified an