Lawyers for a gay and lesbian legal advocacy group have a told a federal appeals court panel that a federal law that denies benefits to married gay couples that heterosexual couples get is discriminatory.

A lawyer for a bipartisan congressional group argued Wednesday in Boston that Congress had a rational basis for passing the law in 1996 when it appeared Hawaii would legalize gay marriage. The attorney says Congress wanted to have one uniform law.

The 1996 federal Defense of Marriage Act defines marriage as a union between a man and a woman, and prevents the federal government from recognizing same-sex marriages.

In 2010, a federal judge in Massachusetts declared a key section of the law unconstitutional. Gay marriage is legal there.