New Orleans attorney John Giffen “Jack” Weinmann served as U.S. ambassador to Finland at the end of the Cold War, lent his name to Tulane University’s Law School building and reigned as Rex.

He died Thursday at 87, leaving his mark in legal, business, civic and diplomatic circles in his hometown and on the world stage.

Weinmann, whose law career with the Phelps Dunbar firm spanned three decades, also served as chairman of the board of Eason Oil Co. in Oklahoma City, Oklahoma, succeeding his father-in-law.

In addition to his post as an ambassador, President George H.W. Bush appointed Weinmann chief of protocol for the White House, a post he held from 1991 to 1993.

“Jack Weinmann was a dear friend who was a true Southern gentleman,” Bush wrote in an email Friday. “He loved his family, and he loved the United States of America. I took advantage of that second ‘love’ and asked him to serve his country as ambassador to Finland and as head of protocol. … It will not surprise those who knew him that he excelled at both.”

In 1996, the Rex organization tapped Weinmann to be king of Carnival.

He was devoted to New Orleans institutions and culture, said Coleman Warner, who wrote Weinmann’s biography in 2011.

Warner cited Weinmann’s deep involvement with Tulane University, where he was chairman of the board for five years; his role as U.S. commissioner general for the 1984 World’s Fair, an appointment made by President Ronald Reagan; and his service to Metairie Park Country Day School, where he was on the board.

“They were very involved,” Warner said of Weinmann and his wife, Virginia. “They wanted to have a positive impact, and they did.”

It was during Weinmann’s appointment to the World’s Fair that he became acquainted with George and Barbara Bush — George Bush was Reagan’s vice president at the time — and he and his wife soon became friends with the political couple.

In 1989, Bush appointed Weinmann U.S. ambassador to Finland, which coincided with the fall of the Berlin Wall. One of his first responsibilities was to convey to Washington the concerns expressed in Swedish and Finnish newspapers about how changes in Germany might spark military conflict in the region, according to his biography.

During his first year in Finland, news broke that Soviet workers had planted listening devices in a new American embassy being built in Moscow. The U.S. responded by turning all the construction work over to American teams, using only building materials trucked in under guard from a secure warehouse in Helsinki, the capital of Finland. It fell to Weinmann and other embassy officials to monitor that process.

His most significant moment on the world stage came in September 1990, when he and his wife organized a summit meeting between Bush and Soviet President Mikhail Gorbachev to address Iraq’s invasion of Kuwait.

The ambassador had less than a week’s notice to organize the summit, which included both presidents and their wives along with a contingent of deputies. The meeting drew 2,300 journalists.

“The United States government has extremely sophisticated communications systems,” Weinmann jokingly told WWL-TV’s Angela Hill in a 1993 interview. “You hear about the hotline and the red telephone and all of that sort of thing. My driver in Helsinki told me that President Gorbachev and President Bush would be there in five days.”

The only son of a lawyer, Weinmann followed his father’s professional path and earned his bachelor’s degree and his law degree from Tulane University, which both his parents had attended.

The university’s Law School building was named for him in 1995 after the Weinmanns made a large financial gift, and he was named Tulane’s distinguished alumnus in 2002.

Weinmann was a vestryman at Trinity Episcopal Church, a founding director of Trinity Episcopal School, a member of the Metropolitan Area Committee and the Bureau of Governmental Research, and a member and director of the Council for a Better Louisiana.

He also served as general counsel for The Times-Picayune from 1968 to 1980. Former publisher Ashton Phelps Jr. described Weinmann as “thoughtful in judgment and meticulous, a good citizen.”

Weinmann and his wife would have been married 61 years on Saturday.

Other survivors include five children, Winston Eason Weinmann, Robert St. George Tucker Weinmann, John Giffen Weinmann Jr., Mary Virginia Lewis Weinmann Coffman and George Gustaf Weinmann, and 16 grandchildren, who called him “Pop.”

Visitation will be from 10 a.m. to noon Tuesday at Trinity Episcopal Church, 1329 Jackson Ave., followed by a funeral service.

Follow Sara Pagones on Twitter, @spagonesadvocat.