By Verna Gates

BIRMINGHAM, Alabama (Reuters) - A civil rights group sued Alabama on Thursday on behalf of a gay man challenging the state's ban on same-sex marriage, arguing he should be able to claim the estate of his husband who died in a car crash.

Paul Hard, an associate professor at a university in Montgomery, is seeking to be recognized as the beneficiary of proceeds in a wrongful death case, but Alabama does not recognize him as a surviving spouse. The couple married in Massachusetts.

"Alabama has created two classes of marriages within its borders and deemed one of those classes - marriages between people of the same sex - to be inferior to the other," said David Dinielli, deputy legal director of the Southern Poverty Law Center, which filed the lawsuit on behalf of Hard.

Same-sex marriage is legal in 17 states and the District of Columbia. Its prohibition is being challenged in states across the country following a U.S. Supreme Court decision last year. In one case, a federal judge in Kentucky on Wednesday ordered the state to recognize same-sex marriages of residents who wed outside the state.

Hard and his husband, David Fancher, were married on a beach in Cape Cod, Massachusetts barely three months before the August 2011 accident. Fancher, 54, died while driving to work, his vehicle plowing into the scattered pieces of an overturned truck near Montgomery.

Hard was listed as the sole beneficiary of Fancher's estate in his will.

The lawsuit in federal court in Alabama seeks to overturn the state's Marriage Protection Act, a 1998 law that bans the recognition of out-of-state gay marriages, and the Sanctity of Marriage Amendment. It says Alabama's definition of marriage violates the equal protection and due process clauses of the U.S. Constitution.

"Marriages are significant, and my marriage is due the same respect as any other," Hard said in a statement on Thursday.

A wrongful death lawsuit has been filed against the trucking companies involved, according to the civil rights group.

The case is Paul Hard v Robert Bentley, in his official capacity as Governor of the State of Alabama, and the estate of David Fancher 2.13-cv-00922-WKW-SRW

(Editing by David Adams and Grant McCool)

[Image: "Two Gay Men After Wedding On A Beach" via Shutterstock]