Definition: The Defense of Marriage Act, or DOMA, is legislation that was signed into law by President Clinton in 1996.
DOMA defines marriage only as the legal union of a man and a woman. DOMA allows states to not recognize same-sex marriage licenses issued by other states. H.R. 3396 Status
Update:
11/10/2011: A vote by the Senate Judiciary Committee was 10-8 to repeal the Defense of Marriage Act. Lacking the required votes in both the Senate and the House of Representatives, no change in the law is expected at this time.Larry Margasak: "Those couples cannot file joint federal income tax returns and take deductions available in traditional marriages. There are no spousal Social Security benefits. They can't take advantage of the Family and Medical Leave law that protects one's job and health insurance during emergency absences. Surviving gay spouses have no protection from estate taxes."
Source: Larry Margasak. "DOMA Repeal Bill Clears Senate Judiciary Committee Vote." HuffingtonPost.com. 11/10/2011.
2/23/2011: The federal Defense of Marriage Act will no longer be defended or supported by the Obama administration.
Attorney General Eric H. Holder Jr.: "The president has concluded that given a number of factors, including a documented history of discrimination, classifications based on sexual orientation should be subject to a more heightened standard of scrutiny. The president has also concluded that Section 3 of DOMA, as applied to legally married same-sex couples, fails to meet that standard and is therefore unconstitutional. Given that conclusion, the president has instructed the department not to defend the statute in such cases. I fully concur with the president's determination."
Source: Valerie Richardson. "Obama gets out of way of gay marriage." WashingtonTimes.com. 2/23/2011.
Statement of the Attorney General on Litigation Involving the Defense of Marriage Act.
Also Known As: DOMA

