By Brendan O'Brien
(Reuters) - Six gay couples in South Dakota filed a federal lawsuit on Thursday challenging the constitutionality of the state's ban on same-sex marriage, court documents showed.
The lawsuit, filed in U.S. District Court in South Dakota, claims the state law violates the U.S. Constitution by depriving the couples of equal protection, due process and the right to travel, according to the complaint.
"Although their sexual orientation bears no relation to their ability to contribute to society, gay men and lesbians have been singled out for discriminatory treatment," the complaint said.
South Dakota Attorney General Marty Jackley was not immediately available for comment.
The lawsuit in South Dakota is the latest in a wave of legal challenges waged by gay marriage supporters since U.S. Supreme Court rulings last year paved the way for gay marriage to resume in California and struck down the Defense of Marriage Act, a federal law that denied federal benefits to legally married same-sex couples.
Supporters have earned key legal victories this month in Oregon, Idaho and Pennsylvania, where judges have struck down state bans on gay marriage.
Governor Tom Corbett, a conservative Republican, said on Wednesday that he would allow Pennsylvania to become the 19th U.S. state to extend the rights of matrimony to gay and lesbian couples.
(Reporting by Brendan O'Brien; Editing by Ken Wills)