The attorney general of Pennsylvania has said she will not defend a state law defining marriage as a union of a man and a woman in court because she does not agree with it.

Thomas Peters, a spokesman for the National Organization for Marriage, said the action shows that the recent U.S. Supreme Court rulings favoring same-sex unions "set a bad precedent" that will allow elected officials "to not represent the will of the people when they find it expedient."

Peters told the Washington Post that the attorney general's move is a "pocket veto" of the law.

Pennsylvania Attorney General Kathleen Kane, a Democrat, said July 11 she believes the 1996 marriage legislation is "wholly unconstitutional." She said she was obligated not to defend the case "because I endorse equality and anti-discrimination laws."

State law requires the attorney general to "uphold and defend the constitutionality of all statutes" to prevent a court from suspending or abrogating them. However, Kane announced that she will not do so for the marriage law.

Government officials' refusal to defend laws supporting marriage between a man and a woman has become a prominent tactic to advance "gay marriage."

In 2011, U.S. Attorney General Eric Holder refused to defend the federal Defense of Marriage Act, which defined marriage for federal purposes as a union of one man and one woman. The House of Representatives then had to fund the defense of the legislation, which passed Congress overwhelmingly in 1996 and was signed into law by President Bill Clinton.

The refusal of state officials in California to defend Proposition 8, a victorious 2008 ballot measure that restored the legal definition of marriage to a union between one man and one woman, led to the U.S. Supreme Court's refusal to hear the case. This in effect affirmed the ruling of California's Supreme Court, which had said the amendment was unconstitutional.

A lawsuit challenging the Pennsylvania marriage act has been filed by the American Civil Liberties Union, representing ten same-sex couples, two minor children, and one person whose same-sex partner died.

The suit cites the U.S. Supreme Court's decision in June that struck down parts of the federal Defense of Marriage Act by a vote of 5-4.

The court ruled that the U.S. government may not restrict the definition of marriage to one man and one woman for the purpose of federal recognition and benefits. It leaves the definition of marriage up to the states.

Gov. Tom Corbett, a Republican, is also named in the Pennsylvania lawsuit. He may instruct his general counsel, James D. Schultz, to defend the law.

The suit also names Pennsylvania's health secretary, whose agency produces marriage licenses that recognize only the bride and the groom, and two county registers of wills whose offices did not give marriage licenses to same-sex couples.

Amy Hill, communications director with the Pennsylvania Catholic Conference, told the Pittsburgh Post-Gazette that it is too early to say whether the conference or other backers of the Defense of Marriage law will file an amicus brief in the case.

The Pennsylvania Catholic Conference has said it will watch the case "closely."

"Marriage is a personal relationship with great public significance – not a private affair – that affects all in society. Marriage is not just about adult relationships, it is the foundation of the family. Every child has a mother and a father. And every child has a basic right to a mother and a father united in marriage," the conference said July 12.

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"While circumstances may prevent a child being raised by his or her own mother and father, marriage is the way society provides for children's needs in ordinary circumstances," it added.