The tech companies also bring in antitrust experts. Amazon, Facebook, and Google each have dozens of in-house lawyers. In January 2020, Amazon hired a former FTC attorney, Amy Posner. In April 2020, Facebook hired numerous government officials, starting with another longtime Federal Trade Commission attorney at the competition bureau.

“What is striking is the number of people who work directly from the agencies for technology companies,” said William Kovacic, a former chairman of the FTC. “That reflects a real change.”

The opportunities to work for tech clients or the tech companies themselves attracted large audiences in a recent mock trial conducted by the American Bar Association. The workshop focused on a fictional large search engine called Knowsmore that was being sued by a smaller search engine that wanted more privacy features. The event was one of the ABA’s best-attended workshops in recent years, said David Reichenberg, attorney at Cozen O’Connor and co-chair of the association’s Litigation Committee.

“Members are becoming more interested in learning more about technology and antitrust law every year,” he said.

There is also more work for lawyers trying to take on the big corporations or represent the government itself. Two law firms reached an agreement last year to represent the state of Texas in its lawsuit against Google. And last month, another law firm teamed up with the District of Columbia attorney general to sue Amazon.

But many of the largest and most renowned companies work for the Silicon Valley giants.

Jonathan Kanter, a longtime antitrust attorney rumored to be a possible candidate to head the Justice Department’s antitrust division, has built his career primarily around working for rivals Google, Facebook, Amazon and Apple. His customer list has included large companies like Microsoft and News Corporation, as well as smaller companies like Yelp and Spotify.

In 2016 he moved to Paul, Weiss, Rifkind, Wharton & Garrison, a well-known law firm. But last year Mr. Kanter’s criticism of Big Tech began to point to conflicts with other parts of the company’s vast portfolio, said two knowledgeable people. In particular, his practice is at odds with the work of Bill Isaacson and Karen Dunn, two attorneys the firm just hired who are known to represent Apple and Amazon, said another person with knowledge of the situation.