Earlier today, a federal district court judge in Los Angeles ruled that President Donald Trump violated the Posse Comitatus Act of 1878 when he sent federal troops into that city to assist ICE agents in carrying out their duties.

With the riots now over, does the decision change anything? Not currently: there are few troops still in LA and the judge’s ruling does not require them to leave just yet. When they do, not much will change either — unless a new wave of rioting breaks out between now and then.

But the ruling is significant as a legal matter and in terms of how it will constrain the President’s policies moving forward. It is a longstanding feature of American law that the civilian authorities are superior to the military, and that the executive should never use the military against the people unless a situation is so out of hand that ordinary law enforcement is impossible. Was that the case in LA a few months ago, when rioters were pelting ICE agents with bricks and rocks and the local police declined to assist them until after the National Guard moved in? It’s not an open-and-shut case.

In the President’s opinion, the normal administration of law was impossible and his agents’ lives were in danger — though not so much so as to invoke the Insurrection Act, which is the major exception to this military-civilian separation. To California Governor Gavin Newsom, the riots were not that spectacular and ICE agents were able to do their jobs just fine. Judge Charles Breyer, a Clinton-appointed-judge (and the younger brother of former Supreme Court Justice Stephen Breyer) agreed with Newsom.

The case will be appealed, and appealed again, and maybe the Supreme Court will have the final say. The line between riot and insurrection is thin and subjective, but it is important. Even those who disagree with Judge Breyer about the facts here will agree that some line in the law must exist that limits the President’s power to send troops wherever he pleases.

Many of Trump’s supporters will believe that he is on the right side of that line, and this decision will only increase their admiration for the man who is trying to do something. And that is fitting, because the biggest reward for Trump of sending in the National Guard — not to mention the Marines — is the appearance (as opposed to the fact) of having done something. ICE agents were under attack in LA, and some protection was needed. But since that day, any troops in the city were there to prove a point, not to do a job.

Breyer’s ruling, if upheld, will crimp Trump’s plans to send troops into New York and Chicago to help with the crime there. But that plan, if it was ever more than an idle musing by Trump, was not likely to pay dividends in any event. Sending in the troops was always about the show of force, not the force itself.

Now, Trump can do what Biden did when he tried to pay off everyone’s student loans and dared the courts to stop him: he will win the emotional argument with a key segment of his supporters without having to actually break the law or do the thing. “I’d fix everything,” he might say, “but one 83-year-old judge in California won’t let me.”

That may be politically smart, but it’s a hell of a way to run a republic.