There are seven days left in his presidency.

President Barack Obama is ending a longstanding immigration policy that allows any Cuban who makes it to U.S. soil to stay and become a legal resident, a senior administration official said Thursday.

The repeal of the “wet foot, dry foot” policy is effective immediately, according the official. The decision follows months of negotiations focused in part on getting Cuba to agree to take back people who had arrived in the U.S…

The official said the Cubans gave no assurances about treatment of those sent back to the country, but said political asylum remains an option for those concerned about persecution if they return…

The official said that in recent years, most people fleeing the island have done so for economic reasons or to take advantage of the benefits they know they can receive if they make it to the U.S.

True to form in his dealings with Cuba, he appears to have extracted zero concessions from Raul Castro in return for this new act of goodwill. “Wet foot, dry foot” is shorthand for a policy in which Cubans caught at sea en route to the U.S. are sent back to Cuba but those who make it to Florida are eligible for residency in the United States, even though they don’t have visas. Why the special treatment for Cubans when normally illegal immigrants caught on this side of the border are sent packing back to their home country? Well, (a) Castro’s Cuba is a prison from which people aren’t free to emigrate, making Cubans who escape refugees, not illegal immigrants, and (b) Cuban-Americans are, of course, a verrrry important constituency in a verrrry important state electorally. In fact, it was the Clinton administration that instituted “wet foot, dry foot” in the mid-90s, mindful of how alienating Cuban-American voters might come back to haunt them. Didn’t help Hillary last year, though.

Why would Obama end a policy that Trump can reinstate in 185 hours or so? Partly it’s symbolic. O wants to signal further normalization in relations with Cuba by treating its immigrants the same way immigrants from other countries are treated. More than that, he probably wants to send a message that Cuba isn’t a gulag to the same extent it used to be — although why he thinks that, given how little Castro promised him by way of human rights reforms as part of their detente, isn’t clear. The idea, though, is that Cubans fleeing the islands should no longer be treated as presumptive refugees because, now that relations with the U.S. have warmed up, conditions there are supposedly better or something. That’s the policy rationale.

The political rationale, I assume, is to box Trump in. Ending “wet foot, dry foot” puts him in an awkward position, after all. If he doesn’t reverse Obama’s new policy, he risks irritating the Cuban-Americans who helped hand him last year’s shocking upset in Florida. If he does reverse the policy, he’ll be reinstating special residency privileges for Cubans who are here illegally — not a comfortable position for a border hawk with a populist-nationalist base to take. And if he tries to defend his decision by classifying Cubans as refugees rather than as illegal immigrants, that’ll open him up to questions of why he’d tolerate accepting refugees from Cuba as a matter of course but won’t accept ones from Syria even when they’ve been closely vetted by government agencies. The point of Obama changing the policy now, more than anything, is to force this issue onto the national radar and box Trump in such that he’ll have to make a high-profile decision one way or another. If O had left office without changing it, Trump could have quietly ignored it and left it in place with no one paying much attention to it even though “wet foot, dry foot” contradicts his own “strong borders” outlook. Now Trump will have to speak up. Whatever he does, he risks alienating some people who voted for him. Not put a fine point on it, but Obama just trolled him.