The American Civil Liberties Union on Wednesday sued the city of Baltimore and four Maryland counties for the right of same-sex couples to marry.
The lawsuit was filed in Baltimore Circuit Court on behalf of nine couples and a man whose partner recently died. The couples had sought marriage licenses and were denied, said Ken Choe of the ACLU's Lesbian and Gay Rights Project, based in New York.
Maryland law specifically defines marriage as between a man and a woman.
In February, Attorney General Joseph Curran sent a memo to state legislators and the 24 clerks of the court reminding them that clerks are not authorized to issue licenses to gay couples.
The ACLU has pending legal challenges in Massachusetts, Oregon, New York, Washington state, California and Nebraska.
Other groups have filed lawsuits in New Jersey and Florida to legalize gay marriage.