The Wisconsin Supreme Court on Thursday 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 high court said the ban did not prevent gay couples from receiving certain benefits.

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 LGBT advocate Fair Wisconsin as the registry's only defender.

According to Fair Wisconsin, more than 2,000 couples have joined the registry.

LGBT advocate Lambda Legal applauded the decision in a statement.

“Gay and lesbian couples in Wisconsin no longer have to fear that the protections they have will be taken away by unnecessary anti-gay legal action,” the group said.

A federal judge in June declared Wisconsin's marriage ban invalid. Van Hollen has appealed the ruling to the Seventh Circuit Court of Appeals.

(Related: Majority support for gay marriage in Wisconsin as federal case heads to appeals court.)