NEW ORLEANS — A federal judge upheld Louisiana’s ban on same-sex marriages on Wednesday, a rare loss for gay marriage supporters who had won more than 20 consecutive rulings overturning bans in other states.
US District Judge Martin Feldman also upheld the state’s refusal to recognize same-sex marriages performed legally in other states. His ruling was the first to uphold a state ban since the US Supreme Court struck down part of the federal Defense of Marriage Act last year.
Feldman acknowledged that his will not be the final word. ‘‘Clearly, many other courts will have an opportunity to take up the issue of same-sex marriage; courts of appeals and, at some point, the US Supreme Court,’’ he wrote. ‘‘The decision of this court is but one studied decision among many.’’
Gay rights advocates said they would carry the case to the US Court of Appeals for the Fifth Circuit, which already has before it an appeal by the state of Texas of another federal judge’s ruling that struck down that state’s gay marriage ban.
In 2004, about 78 percent of Louisiana voters approved an amendment to the state constitution banning gay marriage. Gay marriage is legal in 19 states and the District of Columbia.
Isabel Medina, a professor at the Loyola University New Orleans law school, said she did not see the ruling as a significant road block for gay marriage advocates. Even a Fifth Circuit decision upholding Feldman’s ruling would affect only three states: Texas, Louisiana, and Mississippi, she noted.
It is probable the Texas case will be the first to go to the Fifth Circuit, and cases elsewhere likely will reach the US Supreme Court before Louisiana’s, said professor Carl Tobias of the University of Richmond School of Law in Virginia. Nevertheless, he said, Feldman’s ruling is significant.
‘‘It is important because Feldman is a very experienced federal district judge, and no other federal judge has ruled that way at the trial level,’’ Tobias said. Feldman was appointed to the bench by President Reagan in 1983.
Feldman said gay marriage supporters failed to prove that the ban violates equal protection or due process provisions of the US Constitution. He also rejected an argument that the ban violated the First Amendment by effectively forcing legally married gay couples to state that they are single on Louisiana income tax returns.
Feldman sided with the state, which had argued that the nation’s high court, in the Defense of Marriage Act decision, recognized the rights of state voters and legislatures to define marriage.
‘‘Although opinions about same-sex marriage will understandably vary among the states, and other states in free and open debate will and have chosen differently, that does not mandate that Louisiana has overstepped its sovereign authority,’’ he wrote.
The conservative Louisiana Family Forum praised the ruling.
‘‘This ruling confirms that the people of Louisiana — not the federal courts — have the constitutional right to decide how marriage is defined in this state,’’ Gene Mills, the group’s president, said.
Gay marriage advocates argued that the ban violated constitutional due process and equal-protection rights. ‘‘Every citizen of the United States deserves protection of their rights, uphill climb or not,’’ said Mary Griggs, chairwoman of Forum for Equality Louisiana.
‘It is important because . . . no other federal judge has ruled that way at the trial level.’
Feldman said the Supreme Court decision ‘‘correctly discredited’’ the Defense of Marriage Act’s effect on a New York law legalizing same-sex unions. But he also noted language in the decision outlining the states’ historic authority to recognize and define marriage.
He also said that neither the Supreme Court nor the Fifth Circuit has defined gay people as a protected class in discrimination cases.
‘‘In light of still-binding precedent, this court declines to fashion a new suspect class. To do so would distort precedent and demean the democratic process,’’ Feldman wrote.