South Dakota's ban on same-sex marriage violates the right to due process and equal protection guaranteed under the U.S. Constitution, a federal judge ruled on Monday.
Judge Karen Schreier ruled in favor of six same-sex couples who challenged the South Dakota ban on gay marriage and put her decision on hold pending appeals.
"Plaintiffs have a fundamental right to marry. South Dakota law deprives them of that right solely because they are same-sex couples and without sufficient justification," Schreier said in a 28-page decision.
Schreier's ruling came the same day that the U.S. Supreme Court, which is in the midst of deciding whether to take up the issue of gay marriage, declined to take an early look at a challenge to a Louisiana state ban.
The Supreme Court is still considering whether to take up cases concerning gay marriage bans in Ohio, Michigan, Kentucky and Tennessee, all part of the Cincinnati-based 6th Circuit Court of Appeals ruling that upheld same-sex marriage bans in November.
The 6th Circuit ruling stands in contrast with four other U.S. appeals court circuits that have struck down gay marriage bans, a split that increases the likelihood the U.S. Supreme Court will take up the matter.
South Dakota is under the 8th Circuit U.S. Court of Appeals, which has not ruled on same-sex marriage bans. Schreier cited the lack of an 8th Circuit ruling and a substantial public interest in uniformity and stability in issuing her stay.
"It remains the state's position that the institution of marriage should be defined by the voters of South Dakota and not the federal courts," South Dakota Attorney General Marty Jackley said in a statement.
Same-sex marriage is legal in 36 states, plus the District of Columbia.
"Now is the time for the Supreme Court to take up a case and end marriage discrimination once and for all," Evan Wolfson, president of the same-sex marriage advocacy group Freedom to Marry, said in a statement.
(Reporting by David Bailey in Minneapolis; Editing by Eric Walsh)