From their website:

The Southern Poverty Law Center filed a lawsuit on behalf of Cooper-Harris and her partner, charging that the Department of Veterans Affairs discriminated against them by denying these benefits but granting them to spouses in heterosexual marriages. It also charges the Defense of Marriage Act (DOMA) is unconstitutional because it bans federal agencies from recognizing such same-sex marriages, denying these couples benefits available to couples in heterosexual marriages.