Evelyn Douek, an associate professor at Stanford Law School, said she had initially been skeptical of Mr. Simes’s legal claims but that his arguments were stronger than she had expected. She said his basic premise that the U.S. government cannot use economic sanctions against journalistic entities to “prevent the spread of propaganda” was correct.

“It’s a really important and fundamental principle because one person’s propaganda is another person’s political argument,” she said. “If the government could term anything as propaganda and ban it, that would give it enormous, dangerous power over the public sphere.”

Ms. Douek said that the Biden administration’s work to counter foreign malign influence and the right-wing backlash to those efforts have been a big theme in American politics. But it is a complicated politics: Even as officials in the Trump administration defend free speech, they have also tried to stamp out commentary they do not like, such as criticism of Charlie Kirk after his assassination.

“This moment highlights the importance of the First Amendment protections against the government efforts to crack down on whatever it wants to call propaganda,” Ms. Douek said. “Because once you give that power to the government, you don’t get to choose which government gets to wield that power.”