An organization that opposes same-sex marriage said on Monday that it would file a lawsuit against the State Senate, seeking to overturn the legalization of such marriages and to nullify the hundreds of gay and lesbian weddings that have taken place in New York State since the law took effect on Sunday.

The group, New Yorkers for Constitutional Freedoms, alleges that the Senate violated the state’s open meetings law in the run-up to the vote on the marriage bill and acted improperly in closing the Senate lobby to members of the public.

The lawsuit also asserts that Gov. Andrew M. Cuomo had no basis for issuing a so-called message of necessity, which allowed lawmakers to vote on the marriage bill immediately after the language was drawn up, rather than allowing it to “age” for three days, as is usually required.

“Constitutional liberties were violated,” the Rev. Jason J. McGuire, the executive director of New Yorkers for Constitutional Freedoms, said in a statement. “Today we are asking the court to intervene in its rightful role as the check and balance on an out-of-control State Legislature.”

The complaint (see also below), which is to be filed in State Supreme Court in Livingston County, where Mr. McGuire lives, states: “The plaintiffs in this case seek to preserve not only marriage as the union of one woman to one man, but also our constitutional liberties by acting as a check on an out-of-control political process that was willing to pass a bill regardless of how many laws and rules it violated.”

A spokesman for Mr. Cuomo, Josh Vlasto, said the lawsuit had no merit.

“The plaintiffs lack a basic understanding of the laws of the state of New York,” Mr. Vlasto said.

Spokesmen for the Senate majority leader, Dean G. Skelos, and the state attorney general, Eric T. Schneiderman, declined to comment on the suit.



