Attorney General J.B. Van Hollen said today he won’t defend the state against a lawsuit challenging the state’s new domestic partner registry, a decision registry proponents blasted.

Van Hollen, a Republican, said in a statement that the state Constitution prohibits same-sex couples from holding a legal status that is “substantially similar” to marriage and that he has concluded the registry does just that.

“My decision isn’t based on a policy disagreement,” he said. “ As Attorney General, I prosecute and defend laws that I wouldn’t have voted for if I were a policymaker. That is what I believe the job entails.

"But I will not ignore the Constitution. My oath isn’t to the legislature or the governor. My duty is to the people of the State of Wisconsin and the highest expression of their will — the Constitution of the State of Wisconsin. When the people have spoken by amending our Constitution, I will abide by their command. When policymakers have ignored their words, I will not.”

The Democratic-led Legislature created the registry in the state budget that went into effect July 1. Democratic Gov. Jim Doyle proposed the registry. Wisconsin is the first state in the country to have enacted legal recognition of same-sex couples while also having a constitutional amendment banning gay marriage and civil unions.

Doyle and Rep. Mark Pocan, D-Madison, co-chairman of the Legislature’s powerful budget committee, blasted Van Hollen’s decision.

Pocan said Van Hollen was “shredding the Constitution for political purposes” and that the decision will “force the state taxpayers to fund outside attorneys to defend our Constitution and perform Van Hollen’s job.” 

Doyle echoed those comments in a statement, and a spokesman said he would appoint an outside lawyer to defend the registry. 

Doyle, who announced this week he would not seek re-election in 2010, and Pocan said they believe the registry is constitutional. Van Hollen has been mentioned as a potential GOP candidate for governor in 2010, though he has not said whether he will run. 

Same-sex couples began registering their partnerships in their counties of residence on Aug. 3. 

Wisconsin Family Action has asked the state Supreme Court to prohibit the registry from continuing, saying it violates the constitutional ban on gay marriage and similar unions.

Fair Wisconsin, a gay-rights group, said it would also seek to defend the domestic partner registry.