Judge Stephen F. Williams, a member of the powerful Court of Appeals for the D.C. Circuit for more than three decades, died Friday of complications from the coronavirus, his family and court officials said.

He was 83.

Williams, a senior judge with a professorial manner and special expertise in regulatory and economics law, had been hospitalized since May after becoming sick.

Although Williams went on senior status in 2001, he continued to handle a full caseload until he turned 80 in 2016 and heard cases until earlier this year.

Williams — whose father had been a well-known lawyer and former law clerk to William Howard Taft, who became Supreme Court chief justice after he was president — was a fierce advocate of the philosophy that free markets create free societies. He presided over a host of significant legal cases that touched on energy deregulation, gun control, the powers of independent prosecutors and the Civil Rights Act. He also served on the panel of judges who heard Microsoft’s antitrust appeal, finding that the software giant had abused its Windows monopoly but reversing a lower court’s order to break up the company.

Williams was known for his down-to-earth style. He rode a bicycle to the courthouse, wore casual dress off the bench, including a knit cap at times during cold weather, and brown-bagged vegetarian lunches. He nursed a passion for studying pre-revolutionary Russian history that culminated in two books about the subject. A father of five children, he stopped eating meat after visiting a slaughterhouse, his daughter Susan Ellis, of Chantilly, Va., said.

Among colleagues, Williams was known for consuming almost every legal opinion circulating on a legal question before the court and being unfailingly polite and solicitous toward clerks and staff.

“Truthfully, it breaks my heart. He was my closest colleague. He was my friend. We would have lunch occasionally and talk about everything in the world,” Judge Laurence H. Silberman said Saturday in an interview. “We teased each other because he thought I was too sympathetic to trade unions, and I thought he was too sympathetic to animals.”

Silberman said Williams was a brilliant scholar as well as jurist, and he took good care of himself, but Silberman worried about his daily commute on a bicycle through the streets of D.C.

“I used to constantly try to persuade him to stop riding his bike to court,” Silberman said. But he said Williams was undeterred, either by advancing age or mishaps that sometimes resulted in injury.

Another colleague on the bench, Judge Merrick B. Garland, called him “the kindest of colleagues, eager to engage in vigorous intellectual debate in the most open-minded and non-personal way.”

“He was at heart the professor he had been before taking the bench,” Garland said in an email, “and it is no surprise that many of his superb law clerks have gone on to become professors themselves.”

Williams, the youngest of three children born to Virginia Fain and C. Dickerman Williams, was born in New York City on Sept. 23, 1936, with an ancestry that could be traced to at least two passengers on the Mayflower. He attended Millbrook School and then Yale College, where he graduated magna cum laude in 1958. He earned his law diploma at Harvard Law School in 1961, also magna cum laude. Both Silberman and retired Supreme Court justice Anthony M. Kennedy graduated that same year.

Williams worked in military intelligence with the U.S. Army Reserve, practiced law at Debevoise & Plimpton and later served as an assistant United States attorney for the Southern District of New York.

Williams and his wife, Faith, whom he met while he was in law school, were married in 1966. The family lived in Boulder, Colo., for many years, and Williams taught law at the University of Colorado. He was also a visiting professor of law at UCLA, the University of Chicago Law School and Southern Methodist University. He was a consultant to the Federal Trade Commission. He learned the Russian language with the help of a tutor and traveled there on several occasions in the early 2000s to conduct research and lecture on the rule of law. He wrote several books, including the two about Russian history in which he argued that if Russia had turned to a free-market economy sooner it might have averted the 1917 revolution.

Williams, whose grandfather died in the 1918 influenza pandemic, became sick about two months ago. He was admitted to Sibley Memorial Hospital and put on a ventilator.

Williams is survived by his wife; two sisters, Joan Farr and Honor Ishida; five children and nine grandchildren.

“He had an uncommon love of ideas, an extraordinarily broad-ranging intellectual curiosity, an infectiously good-spirited demeanor, and a joyful sense of humor,” Chief Judge Sri Srinivasan said in a written statement. “We have been immeasurably enriched by the privilege of serving with him.”