Plaintiffs Dara Raspberry, left, and Helena Miller, holding daughter Zivah Raspberry, of Philadelphia, are among the speakers during the announcement of a lawsuit seeking to overturn a 17-year-old state law effectively banning same-sex marriage in Pennsylvania. (Dan Gleiter/AP)

Pennsylvania attorney general Kathleen Kane said Thursday that she will not defend the state in a federal lawsuit filed this week challenging the state’s ban on same-sex marriage, calling the prohibition “wholly unconstitutional.”

Kane’s decision not to fight the lawsuit filed by the American Civil Liberties Union on behalf of 23 Pennsylvania residents places the burden of defending the 1996 law on Republican Gov. Tom Corbett, who supports it. It also reignited a public debate over whether state officials have the right to opt out of legal battles involving same-sex marriage.

In an interview, Kane — who endorsed the idea of gay marriage while running for her post last year — said she was obligated to drop the case “because I endorse equality and anti-discrimination laws.”

“If there is a law that I feel that does not conform with the Pennsylvania state constitution and the U.S. Constitution, then I ethically cannot do that as a lawyer,” she said.

Kane added that the Pennsylvania general counsel, James D. Schultz, was fully capable of defending the governor, who was also named as a defendant in the ACLU lawsuit. “I’m not leaving them high and dry,” she said. “They have their own team.”

Same-sex marriage status in the U.S., state-by-state

Schultz issued a statement saying he and his colleagues “are surprised that the Attorney General, contrary to her constitutional duty under the Commonwealth Attorneys Act, has decided not to defend a Pennsylvania statute lawfully enacted by the General Assembly, merely because of her personal beliefs.”

Schultz added that while awaiting formal “notification and accompanying legal justification, we will continue to review the lawsuit filed by the ACLU.”

Kane now joins the growing ranks of elected officials who have declined to defend gay marriage prohibitions in court. The Obama administration ended up arguing against the Defense of Marriage Act once it reached the Supreme Court, while California officials in both parties declined to defend Proposition 8, a ballot initiative that banned gay marriage in the state.

Last month, the U.S. Supreme Court let stand a lower court ruling that Proposition 8 was unconstitutional, largely on the grounds that backers of the initiative did not have the standing to appeal the lower court’s decision to the nation’s highest court.

In Illinois, Democratic officials have declined to oppose a lawsuit filed last year seeking same-sex licenses from the Cook County clerk. The Thomas More Society, a conservative law firm, has intervened on behalf of five clerks from other Illinois counties who are opposed to gay marriage.

Peter Breen, the society’s vice president and senior counsel, said these sort of “legal games” have forced opponents of same-sex marriage to work to “expose this sort of activity, and then to work aggressively to defend the laws of our states.”

Rob Gleason, chairman of the Pennsylvania Republican Party, released a statement Thursday calling it “unacceptable for Attorney General Kathleen Kane to put her personal politics ahead of her taxpayer-funded job by abdicating her responsibilities.”

“She is blatantly politicizing the highest law enforcement office in our Commonwealth at the expense of a core responsibility of the Attorney General’s office,” Gleason said. “Pennsylvanians are left with the question, if Kathleen Kane’s political beliefs are the standard for law enforcement, what law will she ignore next?”

Mary Catherine Roper, a senior staff attorney for the ACLU of Pennsylvania, said she and others involved in the lawsuit were “celebrating” in the wake of Kane’s announcement.

“To have the highest law enforcement official of the commonwealth come out and say, ‘I agree with you, this law is unjust, that’s huge for us,’ ” Roper said in a phone interview after Kane’s announcement.

Roper said it was “too early to tell” how Kane’s decision would affect the case but said the 10 couples, widow and two children mounting the federal challenge would continue to pursue the case. “We’re ready to roll,” she said.

Kane, the first woman and first Democrat ever elected Pennsylvania attorney general, is a self-described political outsider who has clashed repeatedly with Corbett since taking office.

She has commissioned a probe of how Corbett handled the child sex-abuse case involving former Penn State assistant coach Jerry Sandusky while Corbett was attorney general. In February, she declared that Corbett’s decision to hand over the state lottery to a private British company was illegal because the governor had failed to consult the legislature.

“It’s the role of the attorney general to be an independently elected voice,” Kane said in November after winning the attorney general’s race. “People see politics as a close-knit, good ol’ boy network, and I want to change that starting Day One.”