A Wisconsin appeals court on Friday unanimously ruled the state's domestic partnership registry to be constitutional.

The legislation extends a limited number of protections for gay and lesbian couples, but opponents argued that it violates the state's 2006 voter-approved constitutional amendment banning marriage and anything substantially similar to it for gay couples.

The 4th District Court of Appeals noted that lawmakers who supported the amendment repeatedly assured colleagues that it would not prevent gay couples from receiving some benefits. The campaign to approve the amendment made similar claims.

The state's largest gay rights advocate, Fair Wisconsin, defended the registry in court.

“It demonstrates that Wisconsin really is about trying to treat people fairly,” the group's executive director, Katie Belanger, is quoted as saying by the AP. “That's what we believe in. The amendment was an unfortunate setback for equality in Wisconsin. But we still believe caring and committed couples should have legal protections to take care of each other in times of need.”

The socially conservative group Wisconsin Family Action filed the legal challenge after former Governor Jim Doyle, a Democrat, included the legislation in his 2009 biannual state budget approved by lawmakers.

Doyle appointed private attorneys to defend the law in court after state Attorney General J.B. Van Hollen refused to do so. Van Hollen said he believed the law to be unconstitutional.

Republican Governor Scott Walker fired those attorneys, leaving Fair Wisconsin as the registry's only defender.

In an email to supporters, Wisconsin Family Action President Julaine Appling said her group would appeal the case to the Republican-leaning Wisconsin Supreme Court.

“The people of Wisconsin have strongly affirmed the lifelong, faithful union of a man and a woman as the fundamental building block of civilization,” she said. “Our system of government serves no purpose if politicians can ignore the will of the people with impunity.”