This is another win for the Trump administration at the Supreme Court which will now be able to enforce a tough new rule limiting who can apply for asylum in the United States. From NBC News:

The government can now refuse to consider a request for asylum from anyone who failed to apply for it in another country after leaving home but before coming here. The order means, for instance, that migrants from Honduras, Guatemala, and El Salvador cannot seek asylum in the U.S. if they didn’t first ask for it in Mexico. Justices Ruth Bader Ginsburg and Sonia Sotomayor dissented, saying the court acted too quickly and should allow the case to work its way through the normal judicial process. The administration said the new restriction is needed to respond to “an unprecedented surge” of people who enter the country illegally and seek asylum if they’re caught. But officials said only a small fraction of them are eventually found to be qualified. “The rule thus screens out asylum seekers who declined to request protection at their first opportunity,” said Solicitor General Noel Francisco. He said it allows immigration officials to concentrate on the asylum seekers who most need protection. Immigration courts now face a backlog of 436,000 asylum requests. But given how few are actually granted, it’s reasonable to ask whether those applicants “genuinely fear persecution or torture, or are simply economic migrants,” Francisco said.

This is essentially a safe-third-country agreement just like the one America has with Canada. Under that agreement, anyone seeking asylum from Mexico or Central America must first apply for it in the first country they set foot in, i.e. the United States. The difference here is that the US does not currently have such an agreement with Mexico. In fact, Mexico just politely declined to consider such an agreement yesterday:

[Mexico’s Foreign Minister Marcelo] Ebrard said both McAleenan and President Trump, whom he spoke to briefly after the meeting, asked him about his government agreeing to a “safe third country” accord, which would require most migrants traveling through Mexico to seek asylum or some form of protection there, instead of in the U.S. Under economic pressure from the Trump administration, the Guatemalan government has already consented to a similar controversial agreement that has yet to be ratified by the legislature there. But Ebrard said he told U.S. officials that neither his government or the Mexican Senate would agree to such a deal, stressing that he believes the two sides have accomplished “90%” of the goals they outlined in June, when Mr. Trump was threatening to impose tariffs on Mexican goods unless Mexico did more to stem the flow of migrants.

Despite that, the Supreme Court is allowing the Trump administration to proceed as if such an agreement existed. The administration announced this new rule back in mid-July, but a federal judge in California issued a nationwide injunction against its implementation about 10 days later. Now this Supreme Court ruling has removed that injunction. President Trump celebrated the decision on Twitter:

BIG United States Supreme Court WIN for the Border on Asylum! https://t.co/9Ka00qK1Ob — Donald J. Trump (@realDonaldTrump) September 11, 2019

Acting Director of US Citizenship and Immigration Services Ken Cuccinelli called it “YUGE”:

(1/x) YUGE Win at #SCOTUS today! With only two dissents, #SCOTUS removed the injunctions against @USCIS’ rule requiring asylum seekers to apply for asylum at a country they pass through on their way to the US southern border. While congress continues to do nothing… — USCIS Acting Director Ken Cuccinelli (@USCISCuccinelli) September 11, 2019