A federal judge on Tuesday ruled that President Trump’s attempt to punish an elite law firm associated with his political opposition was unconstitutional and directed the government not to enforce an order Mr. Trump signed in March that had threatened its business.

Siding with WilmerHale, which had sued to block the president’s order, Judge Richard J. Leon of the Federal District Court for the District of Columbia wrote that Mr. Trump appeared intent on coercing the firm, imposing “a kitchen sink of severe sanctions” to drive it to the bargaining table.

The ruling marked the third straight win for the handful of law firms that opted to fight the White House even as several of their peers caved to a pressure campaign and made deals with Mr. Trump to avoid persecution. Judges have already rejected similarly punitive executive orders aimed at the firms Perkins Coie and Jenner & Block, and lawyers representing Susman Godfrey asked a fourth judge earlier this month to issue a final decision in their case.

“The cornerstone of the American system of justice is an independent judiciary and an independent bar willing to tackle unpopular cases, however daunting. The founding fathers knew this!” Judge Leon wrote in a 73-page opinion laced with more than two dozen exclamation points.

“Accordingly, they took pains to enshrine in the Constitution certain rights that would serve as the foundation for that independence,” he wrote. “Little wonder that in the nearly 250 years since the Constitution was adopted no executive order has been issued challenging these fundamental rights.”

So far, federal judges have steadfastly rejected what they have described as an effort by the White House to subjugate the nation’s top law firms.

Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.

Thank you for your patience while we verify access.

Already a subscriber? Log in.

Want all of The Times? Subscribe.