Democratic lawmakers enacted the registry that provides limited benefits to same-sex couples in 2009, three years after Wisconsin voters approved a state constitutional amendment banning gay marriage.
In the five years since, Wisconsin and the nation have seen "a monumental shift in marriage equality," said Katie Belanger, president and CEO of Fair Wisconsin, the state's largest gay rights organization. The group intervened in the case to defend the registry after Gov. Scott Walker and Attorney General J.B. Van Hollen, both Republicans, refused to do so.
A federal judge declared Wisconsin's ban on gay marriage unconstitutional last month, and the 7th U.S. Circuit Court of Appeals plans to hear arguments in the state's appeal on Aug. 26. More than 500 couples married in a weeklong window before the judge's decision was put on hold. Many of those couples had already registered as domestic partners.
Thursday's decision provides important protection for those couples until gay marriage is legalized, Belanger said. But, she added, "Now that this case has come to an end, we are excited to move forward on reaching our ultimate goals of full equality for the entire LGBT community, including marriage equality."
The state Supreme Court ruled in a 2010 lawsuit filed by Julaine Appling, the head of the conservative group Wisconsin Family Action. She said the domestic partner registry violated the state ban on same-sex marriages and anything substantially similar.
But the court said lawmakers and voters who backed the amendment did not mean to bar legislation granting certain rights to same-sex couples. The court pointed to legislative documents and lawmakers' news releases as evidence of this, along with an article Appling wrote in 2005 that said the amendment wouldn't "ban civil unions."
Writing for the court, Justice N. Patrick Crooks also said domestic partnership is not the same as marriage, in which spouses have a legal obligation to support each other financially and enjoy many more rights.
"Marriage is unique in that it is an enforceable contract to which the state is a party," Crooks wrote.
Appling said that while she was disappointed the court disagreed with her regarding the registry's similarity to marriage, she was pleased it recognized marriage as a special institution. She also noted that it didn't question the gay marriage ban.
"What's important in light of what the court issued today is that the court recognized that marriage remains one man and one woman in Wisconsin," she said.
Van Hollen, the state's top lawyer, said that despite the Supreme Court's decision, he still believes the registry is unconstitutional and not defending it was the right choice.
A Dane County judge and state appeals court both previously upheld the registry, which gives listed couples a host of legal rights, including the ability to visit each other in hospitals and make end-of-life decisions.
About 2,300 couples have signed up to be on the registry over the past five years.
Associated Press writer Scott Bauer in Madison, Wisconsin, contributed to this report.