COEUR d'ALENE - A U.S. Supreme Court ruling Wednesday against a federal anti-gay marriage law - known as the Defense of Marriage Act - doesn't directly invalidate an Idaho constitutional amendment banning such unions.

The 2006 Idaho constitutional amendment says that the marriage of a man and woman is the only domestic legal union that is valid and recognized in Idaho. A majority of Idaho voters backed it.

While the Supreme Court ruled the federal government can't discriminate against same-sex couples when determining benefits and protections, the court also made it clear it's not striking down any gay marriage bans like Idaho's.

Still, "Some of the reasoning in the opinion could be used to legally challenge gay marriage bans," said constitutional law professor Richard Henry Seamon of the University of Idaho College of Law.

He pointed to specific language in the Supreme Court's opinion that could open the door to challenges.

The opinion, written by Justice Anthony Kennedy, said, "State laws defining and regulating marriage, of course, must respect the constitutional rights of persons," and continued by citing a 1967 Supreme Court decision which invalidated laws prohibiting interracial marriage.

"The court is reminding us that the U.S. Constitution restricts the states' ability to define and regulate marriage," Seamon said.

Seamon also pointed to Kennedy's line from later in the opinion, where the justice said, "The Constitution's guarantee of equality 'must at the very least mean that a bare congressional desire to harm a politically unpopular group cannot' justify disparate treatment of that group."

Seamon said that idea doesn't just apply to Congress, but also to states.

"You can't pass laws discriminating against groups just because you don't like them," Seamon said.

He added, "The DOMA case is kind of a legal building block for people who want to legally challenge state laws banning gay marriage."

He taught constitutional law this spring at the university, he said, and gay marriage cases generated some emotional and passionate debates among students.

Monica Hopkins, ACLU of Idaho executive director, said in a press release, "As we work through the decision, the ACLU will untangle the more than 1,100 places in federal laws and programs where being married makes a difference - and figure out what that means for same-sex Idahoans who were legally married in other states."

Bob Cooper, a spokesman for Idaho Attorney General Lawrence Wasden's office, said, "(Wasden's) obligation is to defend Idaho state law and the Constitution in court, and he will do that."