The repeal bill, called the Respect for Marriage Act, was introduced this year by California Senator Dianne Feinstein. The bill, which you can read here, states:
"For the purposes of any Federal law in which marital status is a factor, an individual shall be considered married if that individual’s marriage is valid in the State where the marriage was entered into or, in the case of a marriage entered into outside any State, if the marriage is valid in the place where entered into and the marriage could have been entered into in a State."
Yesterday, the Obama administration announced it would support the bill, another step in its evolution toward backing same-sex marriage. In February, Attorney General Eric Holder said the administration would no longer defend the Defense of Marriage Act against the various challenges to it wending their way through the courts, because the administration now considers it to be unconstitutional.
Currently, there is a whole range of federal benefits available to opposite-sex married couples not available to same-sex couples, such as the ability to file joint federal income taxes, and pensions for government employees.