(Saul Loeb/AFP)
Opinion writer

We are now learning that the troops President Trump sent to the southern border are already being brought home, even as the first migrants in the “caravan” begin to arrive. In case you doubt that this whole exercise was a campaign stunt, note that since the election, Trump himself has gone oddly quiet about what he previously claimed was a national emergency.

But make no mistake: The legal battle over the fates of those generally seeking asylum here is very much alive, and the long-term stakes are very high.

new court ruling released early Tuesday underscores those stakes. Buried in the ruling is a warning from the judge: He flatly asserts that Trump is claiming the authority to close down the southern border to asylum claims entirely.

The decision, by Jon S. Tigar of the U.S. District Court in San Francisco, temporarily blocks Trump’s recent executive action barring people from seeking asylum if they did not cross at an official port of entry.

This attempted ban — which was delivered in a presidential proclamation that explicitly invokes the migrants and claims a border “crisis” — is pernicious on its face. As it is, applying for asylum in the United States is perfectly legal. With this proclamation, Trump is simply trying to restrict the ways people can do this. People fleeing violence, persecution or other severe threats don’t always have the opportunity to carefully plan their migration.

The new court decision declares that this order runs afoul of federal law that “has clearly commanded that immigrants be eligible for asylum regardless of where they enter,” noting that the law explicitly says aliens can apply for asylum “whether or not” they entered “at a designated port of arrival.” For a full explainer on what the law says, see this Lawfare piece.

But for our purposes here, there’s something remarkable buried deep in the decision: The judge warns that Trump’s proclamation and the interim rule that went with it actually claim for Trump the authority to shut down the southern border to any and all asylum-seeking.

“The rule itself actually gives the President the ability to issue even more restrictive proclamations” later, the judge’s decision says. “The rule gives the President plenary authority to halt asylum claims entirely along the southern border.”

Trump could go even further later

How does Trump’s action do this? According to immigration lawyers I spoke to, this is a reference to a line in the rule that holds out the possibility of “additional” limitations on asylum later. That line says such limitations might be implemented pursuant to the provision of law that says the president can “suspend the entry” of “any class of aliens” if the president decrees that this would be “detrimental” to our interests.

If that sounds familiar, it’s because it’s the same provision that Trump used to implement his thinly veiled Muslim ban, which has now been upheld by the Supreme Court. Immigration lawyers say the judge is suggesting that Trump is claiming the authority to use this same provision to suspend all asylum claims at the southern border if he so wishes.

“The judge is warning that even more restrictive proclamations could be coming, including halting asylum claims altogether, even those filed by people waiting patiently at ports of entry in Mexico,” Greg Siskind, an immigration lawyer who has written several books on immigration law, told me.

“The judge has sounded a constitutional alarm bell, warning that Trump is claiming unlimited power to bar asylum applications across the entire southern border,” added immigration attorney David Leopold.

“Close the whole thing!”

Is this far-fetched? No, it isn’t. The Post recently reported that Trump was in such a rage about the recent spike in migrant families crossing the border that he privately proposed sealing the border entirely. He exclaimed: “Close the whole thing!”

Trump has also reduced the cap on refugees to its lowest level since the Refugee Act of 1980. And the administration has employed all manner of bureaucratic maneuvering to restrict the number of refugees admitted even further than official limits.

There are all kinds of good reasons for allowing in asylum seekers and refugees. It reaffirms our commitment to international human rights and to providing a safe refuge to those fleeing international horrors. And as a recent Niskanen Center report outlined, refugees tend to assimilate successfully and make positive contributions to the economy. As for Trump’s frequent claim that asylum seekers are evading court hearings and melting into the interior illegally, that, too, is vastly overblown. A flat-out ban on asylum seekers at the southern border would be a humanitarian and diplomatic disaster.

Trump could win this one

It’s true that the courts have blocked many of Trump’s more draconian immigration initiatives. But the Supreme Court did uphold the travel ban. Even though Trump repeatedly revealed the ban’s roots in anti-Muslim animus, the court affirmed Trump’s broad powers to suspend entry to classes of aliens by declaring them detrimental to U.S. interests in a superficially neutral way, regardless of his openly advertised bigoted motives.

In the case of Trump’s asylum restrictions, the law does appear more clear cut, in that it clearly states that people can apply regardless of where they enter, which the new ruling reaffirms. But this is only a temporary restraining order, and Trump appears to be testing how far he can go.

“The district court warned that the President might seek to shut off all asylum applications on the southern border,” national security law expert Peter Margulies told me. “That would mean the end of asylum as we know it.”

Margulies noted that this latest ruling did reaffirm that “the asylum law’s text and structure prevent the president from asserting such boundless power.” However, he added: “But the Supreme Court read the president’s power broadly in the travel ban case. The asylum ban case will show if the Supreme Court regards the statute’s text and structure as imposing any substantial limits on presidential power.”

Of course, Trump may not go this far, and if he does, he may fail. But given what we’ve seen, does anyone want to bet that he won’t try?

Read more:

Dana Milbank: While Trump feasts on Thanksgiving, troops on the border eat rations and await Pancho Villa

The Post’s View: Trump’s latest anti-immigrant gambit: Family separation 2.0

Catherine Rampell: The Trump administration is also punishing legal immigrants. Here’s how.

The Post’s View: Even this ultra-conservative judge rejects Trump’s argument on DACA

The Post’s View: A judge makes the right call on Trump’s would-be transgender ban