The New York State Court of Appeals ruled unanimously (7-0) today to vacate a temporary injunction, issued by the court's Judge Jacob D. Fuchsberg, that had prevented the demolition of the Morosco and Helen Hayes theaters to make way for the Portman hotel project.

At the same time, the state's highest court decided not to hear an appeal by preservationists, led by Natural Resources Defense Council Inc. and Actor's Equity, seeking to overturn a decision by a lower state court that would allow the destruction of the historic theaters.

However, no earthmoving machinery will be moving in immediately. An order by U.S. Supreme Court Justice Thurgood Marshall, which stays a U.S. Court of Appeals ruling, remains in effect indefinitely.

Late yesterday, Jim Hecker, a lawyer for the preservationists, said that attorneys for the hotel developer had filed an emergency application with the Supreme Court to lift Marshall's injunction. It was not known when action will be taken on the application.

On Feb. 26, after lengthy litigation, the federal appeals court in New York ruled that the theaters could be demolished. Shortly after that ruling, attorneys for the preservationists obtained the stay from Marshall in an effort to bring the issue before the full Supreme Court.