Two citizens’ rights groups filed paperwork Tuesday to intervene in a lawsuit seeking to declare the state’s recent authorization of domestic partner registry unconstitutional.

Fair Wisconsin, represented by Lambda Legal, and the American Civil Liberties Union filed separate motions to intervene in the lawsuit filed by Wisconsin Family Action, a group that advocates for traditional family structures in Wisconsin.

The lawsuit holds the domestic partner registry Gov. Jim Doyle signed into law in July violates the 2006 amendment that recognizes marriage as an institution between a man and a woman.

By filing motions to intervene, both Fair Wisconsin and the ACLU hope to guarantee the protections provided to same-sex couples in the domestic partner registry remain intact.

“[The registry] is a very commonsense piece of legislation that most people in Wisconsin understand and support,” said Katie Belanger, executive director of Fair Wisconsin.

“What’s at stake here is some of the most basic, commonsense protections that people really need,” Belanger said.

Under the domestic partner registry law, couples are afforded about 40 of the 200 protections traditional married couples receive, according to Christopher Clark, senior staff attorney in the Midwest regional office of Lambda Legal.

The registry provides same-sex couples the legal rights to make end-of-life decisions, visit one another in the hospital and receive family medical leave benefits, among other protections.

Clark said the central issue in the case is wording in the 2006 amendment which prohibits the state from recognizing any legal status that is “substantially similar” to that of marriage for same-sex couples.

Wisconsin Family Action believes the domestic partner registry specifically violates this portion of the amendment by providing same-sex couples with a status equivalent to marriage.

“It violates the amendment because it creates a new legal status that is virtually the same as same-sex marriage,” said Julaine Appling, president of Wisconsin Family Action and plaintiff in the case.

Clark disagreed, calling the idea that marriage and domestic partnership are substantially similar “a completely bogus argument.”

The lawsuit is also drawing scrutiny from Fair Wisconsin and the ACLU because it was initially filed through the state Supreme Court instead of beginning in trial court as is traditional practice.

The next step is for the Wisconsin Supreme Court to decide whether it will hear the case as an original action case or send it to a trial court, according to Clark.

Couples already signed up for the registry, meanwhile, feel hurt by Appling’s petition. Judi Trampf, a Madison woman who has signed up for the registry, is represented by the ACLU in its motion to intervene in the petition. Trampf said she feels angry at the prospect of losing the domestic partner benefits she currently has as result of the registry.

“We have so few rights as gay and lesbian people and the ones that were given to us via the domestic partnership registry are important, and the thought of having them taken away is a real threat,” Trampf said.