Only a few weeks after the Justice Department announced withdrawal of its support for the federal Defense of Marriage Act, legislation to repeal it was introduced in the House of Representatives. Specifically, on March 16, 2011 Rep. Jerrold Nadler (D. N.Y.) re-introduced the Respect for Marriage Act, which he first sponsored in 2009. The legislation has the support of over 100 co-sponsors in the House, including four openly gay members of Congress. A version of the bill shortly is expected to be introduced in the Senate by Sen. Dianne Feinstein (D. California). This will be the first time that the Senate has entertained a bill to repeal DOMA, which since 1996 has limited the rights and protections of federal laws to legally married, opposite sex spouses.
Prior to DOMA, marital status was decided at the state level, and if the Respect for Marriage Act becomes law this again will be the case. If a same-sex couple legally was married in a state that permits such unions, such as Massachusetts, the couple would have equal treatment under federal law as an opposite-sex married couple. Couples who are registered domestic partners or in civil unions would not have spousal status for federal purposes unless they also legally were married under state law. Lamda Legal prepared a concise summary of the likely impact of the Respect for Marriage Act; you can read that summary here.