We shouldn’t minimize the awfulness of this order, which is militarily unjustified and based on nothing but the bigotry of Trump and some of his supporters. Trump’s assertion that the military “cannot be burdened with the tremendous medical costs and disruption that transgender in the military would entail” was utterly ludicrous. According to a study by the Rand Corp., the medical costs associated with the few thousand transgender service members are between $2.4 million and $8.4 million a year, or about 1/1000th of 1 percent of the Pentagon budget. Another report by the Palm Center estimated the cost of removing transgender troops at $960 million, or more than 100 times the medical costs that Trump is supposedly concerned about. The truth is that transgender troops are serving honorably and capably, they make up a tiny portion of the military, and accommodating them is relatively simple and well worth the cost.

But this could wind up being one of the rare cases where Trump has an impulse and bleats it out on Twitter, and it actually winds up becoming policy. That makes it a rare exception — one that shows just how constrained Trump is in more general terms.

Even on the things that are important to him, nothing has been as easy as Trump hoped or believed. He thought he could get rid of the Affordable Care Act and replace it with “something terrific,” but that didn’t work out. He thought that by now he’d have built a big, beautiful wall on our southern border, and not only hasn’t it happened, he has been reduced to threatening to shut down the government if it doesn’t get started. (The promise that Mexico would pay for it has disappeared.) He thought he could renegotiate NAFTA and jobs would come streaming back to the United States, but that turns out to be a long and involved process that won’t produce the immediate gratification he was after. He has to deal with a Congress that won’t do what he says, policy questions that are more complex than he ever imagined and courts that keep getting in his way.