A federal judge blocked President Donald Trump's administration Wednesday from enforcing portions of an executive order designed to punish a prominent law firm linked to Democratic-funded opposition research during the 2016 presidential campaign into ties between the Republican candidate and Russia.

WASHINGTON—A federal judge blocked most of a White House executive order punishing Perkins Coie, saying the administration had put itself at odds with the First Amendment by targeting the law firm based on President Trump’s dislike of its work for his political opponents.

The president’s use of government power to punish firms is seen by some legal experts as undercutting a basic tenet: the right to a strong legal defense.