"I cannot ethically defend the constitutionality of Pennsylvania's (law banning same-sex marriage), where I believe it to be wholly unconstitutional," Kathleen Kane announced to reporters at the National Constitution Center in Philadelphia on Thursday.
Under Pennsylvania law, it is the attorney general's duty to defend the constitutionality of state laws. But the law also says the attorney general may allow lawyers for the governor's office or executive-branch agencies to defend a lawsuit if it is more efficient or in the state's best interests.
Kane, a Democrat who supports same-sex marriage, said she will leave the job to Corbett, a Republican who opposes same-sex marriage. Both were named in a lawsuit filed in federal court Tuesday seeking to overturn the law and legalize same-sex marriage in Pennsylvania.
Corbett's office has declined to comment on the lawsuit.
Pennsylvania is the only northeastern state that does not allow same-sex marriage or civil unions.
A 1996 state law defines marriage as a civil contract in which a man and a woman take each other as husband and wife. The state also does not allow civil unions or recognize same-sex marriages from other states that allow it.
The plaintiffs in the lawsuit are a widow, 10 couples and one of the couples' two teenage daughters. The group includes four couples who were legally married in other states but whose marriages go unrecognized by Pennsylvania.
Same-sex marriage is legal or soon will be in 13 states. The lawsuit asks a federal judge to prevent state officials from stopping gay couples from getting married and to force the state to recognize the marriages of same-sex couples who wed in other jurisdictions.
Lawyers in the case believe it is ultimately bound for the U.S. Supreme Court, probably along with similar cases in other states, and could force the high court to rule on the core question of whether it is unconstitutional to deny same-sex couples the right to marry.