In the summer of 1984, at the Republican National Convention in Dallas, Gregory Johnson burned an American flag to protest the policies of President Ronald Reagan.

“It was a way to speak to the people of the world,” Mr. Johnson said last week, a few days after President Trump issued an executive order that sought to undermine his landmark Supreme Court victory, Texas v. Johnson. By a 5-to-4 vote in 1989, the court said Mr. Johnson’s burning of the flag was political expression protected by the First Amendment.

Mr. Johnson, now 68, said protests like the one in Dallas were even more urgent in the Trump era. “Do you want to live in a country,” he asked, “that’s based on coerced, forced, compulsory patriotism?”

Mr. Trump’s order urged prosecution of flag burnings “to the fullest extent permissible” by invoking laws not aimed at speech, and it instructed officials to pursue deportation of noncitizens who burn American flags. The order only indirectly challenged the 1989 ruling, however, telling the attorney general to “pursue litigation to clarify the scope of the First Amendment exceptions.”

Mr. Johnson said he had not planned to burn a flag in Dallas. But when someone handed him one, he said, it seemed fitting.

“That flag,” he said, “is a symbol of American empire and plunder and murder going back to slavery in this country, and 100 years of Jim Crow segregation and all the lynching and the theft of half of Mexico.”