A New York State Supreme Court Justice today ruled in favor of a taiwanese athlete seeking to compete in the upcoming Winter Olympics here using his traditional Nationalist Chinese flag and emblem. Officials of the Lake Placid Organizing Committee (LPOCC) said they would appeal the decision.

The latest chapter in a long-running legal battle over Taiwanese athletes' rights to compete as represenatives of the Republic of China and use their Nationalist flag and anthem briefly overshadowed the major political controversy facing the beleaguered International Olympic Committee (IOC) -- a U.S. proposal taht the Summer Olympics be moved from Moscow, postponed or canceled in response to the Soviet invasion of Afghanistan.

President Carter today designated Secretary of State Cyrus R. Vance as his representative to open and address the IOC session that will consider this proposal.

Vance will make the welcoming speech at Saturday night's formal opening of the IOC session, and may use the occasion to present the Carter administration's opposition to U.S. participation in Moscow if Soviet troops remain in Afghanistan beyond Feb. 20.

Usually the opening of an IOC session by a high-level government official of the host nation is a low-key ceremonial affair.

The is the only phase of IOC proceedings open to reporters, however, and Vance may take the opportunity to spell out publicly to the 89-member IOC the U.S. position regarding the Moscow Games.

According to sources, Vance who will arrive here Saturday and depart the next day, has requested a private meeting with IOC President Lord Killanin and other high-ranking members of the autonomous group that owns and oversees the Games.

If the IOC, which historically has resisted all government intrusions into its affairs, rejects such a meeting, the sources said, Vance will use his opening remarks to emphasize the U.S. view that Soviet agression in Afghanistan has rendered Moscow an unsuitable site for Games intended to promote peace and international goodwill.

United States Olympic Committee (USOC) officials today met privately with Killanin, but declined to comment on their discussions. On Friday they will present to the IOC executive board a resolution asking for the Games to be moved from Moscow, postponed or canceled. On Monday the same presentation will be made to the full IOC session.

The resolution, requested by President Carter, was approved unanimously by the USOC executive board last month.

White House counsel Lloyd Cutler and deputy counsel Joseph Onek were to meet with USOC officials here Friday.

Meanwhile, the Associated Press reported that none of the 20 IOC members it had contacted in Lake Placid showed signs of supporting the U.S. proposal. "We can't even think of moving the games because Moscow has not broken an Olympic rule," said Lance Cross of New Zealand, a member of the IOC's nine-man executive board.

Regarding the participation of the Taiwanese in the Winter Games, which begin Wednesday, the Lake Placid committee said it hoped its appeal of today's ruling could be heard by Saturday.

Justic Norman L. Harve, in a 10-page decision, ruled that Taiwanese cross-country skier Liang RenGuary should be allowed to carry the traditional blue-and-red flag of the Republic of China, to enter the Olympic Village, and to use the anthem of his island nation.

The IOC, which until two months ago recognized Taiwan as the Republic of China, admitted the People's Republic of China into the Olympic family Nov. 26, and said Taiwan could compete only as the Chinese Taipei Olympic Committee, using a special flag and anthem to be approved by the IOC.

Taiwan refused to accept this solution to the 30-year-old "two-Chinas" dispute, and sued the Lausanne-based IOC in a Swiss court. The court ruled for the IOC, and a three-judge appellate panel upheld the decision Monday.

However, in the suit brought in New York against the Lake Placid group, Harvey ruled that "the defendant and the IOC must abide by the Constitution of the United States and the laws of the State of New York," and that there was "neither logic nor merit" to the IOC's shift in Taiwan's status.

"It is the opinion of the court that the IOC had no authority to make that determination," the judge said.

It was not immediately clear whether Harvey's ruling applied only to the athlete who filed the suit or to all the Taiwanese athletes seeking to enter the Winter Games. Nor was it clear whether his ruling, if upheld, could be enforced.

LPOCC officials said they are confident the ruling would be overturned before the start of the Games. The IOC said it would have no comment until its attorneys reviewed the decision.