1 U.S.C. § 7 - U.S. Code - Unannotated Title 1. General Provisions § 7. Marriage

(a) For the purposes of any Federal law, rule, or regulation in which marital status is a factor, an individual shall be considered married if that individual's marriage is between 2 individuals and 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 between 2 individuals and is valid in the place where entered into and the marriage could have been entered into in a State.

(b) In this section, the term “State” means a State, the District of Columbia, the Commonwealth of Puerto Rico, or any other territory or possession of the United States.

(c) For purposes of subsection (a), in determining whether a marriage is valid in a State or the place where entered into, if outside of any State, only the law of the jurisdiction applicable at the time the marriage was entered into may be considered.