Mayor Bloomberg wants to convince New Yorkers that the debate over whether same-sex couples should be allowed to marry is an issue lawmakers in Albany should decide, instead of an individual judge in Manhattan. If he didn’t challenge that judge’s ruling of last Friday, he said, New York City would have been at the center of a complicated legal battle that he felt it was his duty as mayor to avoid.

Mr. Bloomberg told reporters in Williamsburg yesterday that he was concerned about same-sex couples’ getting marriage licenses in New York and then “six months, or one year later, or two years later, finding out it’s meaningless.

“That,” the mayor said, “is not in anybody’s interest.”

His aides have said the issue of constitutionality is for the courts to decide, and the question of whether same-sex marriages is good policy should be left to the legislature in Albany. The matter returned to the headlines last week when a New York County judge, Doris Ling-Cohan, ruled that a law denying gay couples the right to marry violates the state Constitution.

Before last week, a 1993 estate case in Brooklyn, which was related to the survivorship benefits of a same-sex long-term partner, had set the standard for the issue of gay rights in New York. A gay man, William T. Cooper, died without a full will, and his long-term male partner tried to claim the rights of a surviving spouse.

Judges at Long Island decided that the term “surviving spouse” in the state statute did not include an unmarried long-term same-sex partner. The court went on to say the estate section of the law they used in making their decision did not fly in the face of the state’s Constitution.

In her ruling last week, Justice Ling-Cohan decided the opposite. Five gay couples who sued the city last year for refusing to issue them marriage licenses had been unjustly prevented from getting married, she ruled. They had a right to marry under the state Constitution. The judge ordered the county clerk to issue marriage licenses to same-sex couples within 30 days. In the view of many lawyers, Mr. Bloomberg had no choice but to appeal her decision.

“If Bloomberg hadn’t appealed, you could suddenly get married in New York regardless of sexual orientation, and that would have meant chaos,” a partner at the Proskauer, Rose law firm, Peter Sherwin, said. “The mayor would have been imposing this decision on the entire state. Suddenly New York State would have to work to change its tax forms so same-sex couples could file their taxes jointly. There are huge lists of laws that would have had to be modified overnight. To have that all of a sudden go into effect would raise all kinds of legal issues.”

Until now, only a handful of cases have directly challenged the constitutionality of New York’s domestic-relations law, and other courts have essentially deferred to the precedent set in the 1993 Cooper case. The question now is what will happen next.

As early as today, the city’s lawyers will file a Notice of Appeal, the paperwork that will formally ask a higher court to look at the soundness of Justice Ling-Cohan’s legal reasoning.

The city will ask that the appeal go directly to the state’s Court of Appeals – unlike most states, in New York the highest court is not the Supreme Court, but the Court of Appeals. The city will ask for a statewide clarification of whether it is constitutional to prevent same-sex couples to marry.

Filing the appeal prevents the Ling- Cohan ruling from taking effect. Filing a friend-of-the-court brief instead, as some Bloomberg critics have suggested the city could have done, would not have stopped the 30-day clock, lawyers said.

The appeal, if the Court of Appeals decides to take it, could be decided as early as this spring.

“I know the mayor has taken a lot of flak for this,” Mr. Sherwin, who is gay, said. “But I think he is trying to inject some certainty into this debate. We know that the New York Court of Appeals will rule definitively on this. It is just a question of when. If they don’t do it from this case, they will do it from one of these other cases that are pending.”