This DOMA law was signed by Pres. Bill Clinton, and now defended by Pres. Barack Obama:
The Obama Justice Department yesterday filed a brief urging a California district court to dismiss a little-known constitutional challenge to DOMA filed in late 2008 by a married gay couple.Obama was elected with a promise to oppose same-sex marriage, so this should not be surprising.
I did not know it, but the US Supreme Court has already ruled on whether the US Constitution requires same-sex marriage in Baker v Nelson (1972).