In a novel legal attack on a state's same-sex marriage ban, a liberal Protestant denomination on Monday filed a lawsuit arguing that North Carolina is unconstitutionally restricting religious freedom by barring clergy from blessing gay and lesbian couples.

The lawsuit, filed in a U.S. District Court by the United Church of Christ, is the first such case brought by a national religious denomination challenging a state's marriage laws. The denomination, which claims nearly 1 million members nationwide, has supported same-sex marriage since 2005.

"We didn't bring this lawsuit to make others conform to our beliefs, but to vindicate the right of all faiths to freely exercise their religious practices," said Donald C. Clark Jr., general counsel of the United Church of Christ.

The denomination argues that a North Carolina law criminalizing the religious solemnization of weddings without a state-issued marriage license violates the First Amendment. Clark said North Carolina allows clergy to bless same-sex couples married in other states, but otherwise bars clergy from performing "religious blessings and marriage rites" for same-sex couples, and that "if they perform a religious blessing ceremony of a same-sex couple in their church, they are subject to prosecution and civil judgments."

The United Church of Christ is joined in the case by a Lutheran pastor, a rabbi, two Unitarian-Universalist ministers and a Baptist pastor, as well as by several same-sex couples. They said that North Carolina's marriage law "represents an unlawful government intervention into the internal structure and practices of plaintiffs' religions."

The defendant in the case, North Carolina Attorney General Roy Cooper, has said he believes his state's ban on same-sex marriage should be lifted, but has also pledged to defend the state's laws "when legal arguments exist."

The case is one of nearly 70 around the country challenging same-sex marriage bans, according to Evan Wolfson, founder and president of Freedom to Marry, which supports same-sex marriage. Wolfson said many religious leaders have supported same-sex marriage, but the UCC litigation is unusual, reflecting North Carolina's strenuous efforts to prevent same-sex marriage.

But Tami Fitzgerald, executive director of the North Carolina Values Coalition, which opposes same-sex marriage, derided the legal action as "the lawsuit of the week filed by those who want to impose same-sex marriage on North Carolina."