In June 2013, the United States Supreme Court concluded in United States v. Windsor that section 3 of the Defense of Marriage Act (DOMA) was unconstitutional. Section 3 stated that marriage referred only to a union between a man and a woman. Thereafter, President Obama asked government departments to implement the Court's decision.
The Department of Labor announced last Wednesday that same-sex marriages will be recognized under ERISA. ERISA is the law that governs employee benefit plans. Thus, for purposes of employee benefit plans, the term "spouse" will include a person married to a person of the same sex who were legally married in a state that recognizes such marriages, but who are domiciled in a state that does not recognize same-sex marriages. The term "marriage" includes a same-sex marriage legally recognized as a marriage under any state law. However, "marriage" does not include a domestic partnership or civil union that is not recognized as a marriage.
The Department of Labor concluded that considering all marriages as valid regardless of the persons' state of domicile will make administration of benefit plans less complicated.
DOL Technical Release 2013-04 can be found here: http://www.dol.gov/ebsa/newsroom/tr13-04.html