A representative of New Yorkers for Constitutional Freedoms and a rabbi said in a lawsuit filed in state court that New York's Senate violated its own procedures and the state's open meetings law when it approved the bill last month.
The lawsuit claims that the Senate prevented lawmakers who opposed the bill from speaking and that the Senate didn't follow procedures that require a bill to go through appropriate committees before a full Senate vote.
Opponents of the gay marriage law had promised lawsuits.
"We should have an open and deliberative process," the Rev. Jason McGuire, executive director of New Yorkers for Constitutional Freedoms, told The Associated Press. "If truly the legislation can stand on its own merits then it should be able to withstand being deliberated publicly."
Spokesmen for Senate Republicans and the state's attorney general declined to comment.
Hundreds of gay couples got married starting Sunday as New York became the sixth and largest state to legalize same-sex weddings.
Ceremonies were held around the state, mostly in New York City, where the day's celebration was tempered by a protest in which thousands of opponents marched to the United Nations.
On Monday, a mass wedding in Niagara Falls saw 46 same-sex couples exchange vows, and 100 more couples were expected to marry en masse at Bethpage State Park on Long Island on Tuesday. Monday night's performance of "Hair" on Broadway was to be followed on the St. James Theatre stage by the weddings of three theater couples, with actor Colman Domingo, who was ordained for the occasion, officiating.
"`Hair' has never been just a show; its message of change and hope and inclusion is one we try to live, not just preach," said Oskar Eustis, artistic director of the Public Theater, one of the producers of the show. "The entire company of this amazing production went to Washington to march for marriage equality and now we are honored to help these loving partners change the world, couple by couple."
In Niagara Falls, a light drizzle fell as partners from New York, Pennsylvania, Ohio and Arkansas and ranging in age from their 20s to their 60s gathered for the ceremony. A handful of opponents clasped hands in a circle and prayed quietly nearby.
"Everything we've felt and lived in our lives, it's legal," Candy Casey, of Buffalo, said after marrying her partner of 21 years, Diane Wnek. "To be able to say to the rest of the world, `Yes we count, we're legal."'
Casey, 52, and Wnek, 59, have been wearing wedding rings for 20 years, hoping the state would someday legalize their union. They married quickly after the law changed, anticipating legal challenges such as the one filed Monday.
"We've always known our love is legitimate and now the rest of the world knows," Wnek said.
Within moments of their wedding, they and other couples set their sights on Washington and efforts to repeal the federal Defense of Marriage Act, which continues to restrict benefits like joint federal tax returns, federal health plans for spouses and access to spouses' federal pensions.
"We still have work to do," Casey said.
The New York bill was adopted the night of June 24, the last day of the legislative session after days of closed-door negotiations involving Gov. Andrew Cuomo and key lawmakers. The lawsuit claims that Cuomo improperly waived the three-day waiting period between a bill's introduction and a vote. Such waivers are common in Albany for negotiated bills.
The debate on the night of the vote was severely restricted in a manner unprecedented in recent years.
The Senate's Republican majority allowed unlimited time for supporters of the bill to speak, including Democratic Sen. Thomas Duane who sponsored it, and Republican Sen. Stephen Saland, who provided the pivotal vote. But Lt. Gov. Robert Duffy, who was presiding over the Senate, repeatedly cut off Democratic Sen. Ruben Diaz Sr., a minister who led the opposition. Diaz sought to persuade his colleagues to vote "no."
The lawsuit also claims that promises of campaign contributions were made to Republican senators who voted for the bill.
July 15 financial filings with the state Board of Elections showed that Cuomo and the four Republican senators who voted for gay marriage received large campaign donations from groups and individuals who pushed for it to be legalized.
On the night of the vote, Cuomo wouldn't say why his chief of staff spoke with Duffy on the Senate floor just before debate was cut to minutes, when Senate rules provide for four hours of debate on bills.
Rules can't be changed unless a majority of the Senate votes to change them.
Cuomo, Duffy and Senate leaders didn't respond Monday to requests for comment on the rules and how they were applied the night of the vote.
With the legal challenge ramping up, the couples married at Niagara Falls seemed unaffected as they laughed, danced and snapped photos during a champagne and cake reception under a white tent.
"I don't know after today how people can take marriage for granted," said Sharon Gerbracht, 49, who married her partner of 21 years. "It's such a privilege."
"The minute we said our vows," her partner, Nancy Gerbracht, said, "we were overwhelmed to have these rights we never thought we'd have in our lifetime."
Officials in Niagara Falls hope the ceremony will help the city perched on one of the world's great natural wonders recapture its storied identity as the world's "Honeymoon Capital."
The city has made the most of its nickname, the Rainbow City, playing on the rainbow symbol of gay pride. With its Rainbow Bridge to Canada, Rainbow Boulevard and Rainbow-themed businesses, it hopes to attract some of the business same-sex weddings will provide.
Mayor Paul Dyster had the falls lit up in rainbow hues as he officiated at the city's first same-sex wedding, timed to wrap up early Sunday at one second past midnight. He gave brides Kitty Lambert and Cheryle Rudd a picture of the illuminated falls as a gift.
Associated Press writers Michael Gormley and Michael Hill contributed to this report from Albany.