George Nicolau, who ruled against baseball owners in two collusion cases and served as president of the National Academy of Arbitrators, died Jan. 2 at a hospital in Manhattan. He was 94.

Gene Orza, the former chief operating officer of the Major League Baseball Players Association, confirmed the death but did not provide a cause.

Mr. Nicolau took over as the independent chairman of Major League Baseball’s arbitration panel in 1986 after owners fired Thomas Roberts, who had ruled that teams acted in concert against free agents after the 1985 season.

Mr. Nicolau also decided teams acted in concert against free agents after the 1986 and 1987 seasons. The cases were settled in 1990 when management agreed with the players’ union to pay those players affected $280 million.

In another notable decision, Mr. Nicolau decided in 1987 to cut short a season-long suspension of free agent pitcher LaMarr Hoyt to 60 days. Hoyt had been penalized for his involvement in three illegal drug incidents during 1986.

Mr. Nicolau decided to reinstate Steve Howe in November 1992, overturning a lifetime ban imposed by Commissioner Fay Vincent five months earlier. The pitcher was suspended seven times for infractions related to drug or alcohol use. Mr. Nicolau determined Howe had a psychiatric disorder and the commissioner’s office didn’t adequately test him.

In a case with impact for many players, he ruled in 1986 against pitcher Dennis Lamp’s grievance that Toronto held him out of games so he could not accumulate bonuses hinged to his games played.

Mr. Nicolau also served as the independent arbitrator for the NBA and the National Basketball Players Association from 1979 to 1981 and the NHL and the NHL Players Association from 1993 to 1996. Mr. Nicolau remained baseball’s panel chairman until 1995, when he was replaced by Nicholas Zumas.

Mr. Nicolau, the son of Greek immigrants, was born in Detroit on Feb. 14, 1925, and grew up in Jackson, Mich.

He served in the Army Air Forces during World War II, flying four missions in B-17 Flying Fortresses over Germany as a bomber navigator. On the second mission, the plane was to bomb an airfield in Evreau but went off course and wound up over Nazi-occupied Paris. But the pilot refused to believe it.

“I know the Eiffel Tower when I see it,” Mr. Nicolau said during a 1990 interview with the Associated Press, recalling what he told the pilot.

During his fourth mission, Mr. Nicolau got hit with flak en route to Leipzig, Germany. His left leg was badly injured. “It was hanging by a thread two days later,” he said. “The bone was shattered.”

After a year’s convalescence, he attended the University of Michigan on the GI Bill and graduated in 1948 with a degree in political science and economics. He received a degree from Columbia Law School in 1951 and became a labor lawyer for 12 years.

In the 1960s, he worked as deputy director for special projects in the U.S. Peace Corps’ Washington Office, as deputy regional director of the U.S. Office of Economic Opportunity, as the first commissioner of New York City’s Community Development Agency, and as executive director of the Fund for the City of New York.

At the behest of noted mediator Theodore Kheel, Mr. Nicolau became executive director of the Institute for Mediation and Conflict Resolution in 1970. He joined the National Academy of Arbitrators in 1975, saying he was influenced do to so by Peter Seitz, who headed baseball’s arbitration panel at the time and would go on to strike down the reserve clause that December in the Andy Messersmith-Dave McNally case.

In addition to sports, Mr. Nicolau arbitrated disputes in aviation, communications and entertainment. He was a past board president of the National Academy of Arbitrators.

His wife, the former Siobhan Oppenheimer, died in 2013. Survivors include two sons; three stepchildren; and six grandchildren.

— Associated Press