President Donald Trump says that the Supreme Court has given him a big win on asylum. Don't be so sure.

True, by a vote of 7-2, the justices allowed Trump's new asylum regulation to go into effect - the one that says you can't apply for asylum at the southern border if you've passed through Mexico and haven't tried and failed to get asylum there.

But reversing the lower courts that blocked the regulation, pending litigation, isn't the same thing as upholding it as lawful. The court of appeals still has to issue a final ruling on whether the rule violates federal immigration statutes and whether the government was authorized to issue it without first seeking notice and comment from the public.

Then, after final rulings from the appellate court, the Supreme Court will surely weigh in - and still might strike it down.

This may be precisely why two liberal justices, Stephen Breyer and Elena Kagan, did not dissent from the court's decision. Breyer and Kagan are extremely unlikely to uphold the Trump asylum regulation when it eventually makes its way to the Supreme Court for a judgment on the merits of its legality. They almost certainly made a strategic judgment to hold their fire for now. Their choice not to join the dissenting opinion written by Justice Sonia Sotomayor, and joined by Justice Ruth Bader Ginsburg, could be a signal to Chief Justice John Roberts that it is perfectly logical to allow the rule to go into effect for now, while still ultimately voting that it is unlawful.

If this all sounds technical, that's because it is. Yet, as is often the case at the Supreme Court, the stakes of the technical details are highly significant.

Start with the policy itself. Promulgated by the attorney general and the secretary of homeland security on July 26, 2019, the new rule says that Central Americans who reached the southern border of the United States can't apply for asylum unless they were previously denied it in Mexico or another country. In structure, the regulation bears a resemblance to rules that are in place in Europe, where (essentially) asylum seekers are required to apply for asylum in the first country in which they are formally registered.

The main legal problem with the rule is that federal immigration law says that any person who is "physically present in the United States or who arrives in United States … may apply for asylum." That doesn't seem to allow for a contradictory rule that limits who can apply.

The same immigration law does say that you can't apply for asylum if the attorney general determines that you could be resettled in a safe third country - that is to say, not the one you are fleeing - or if you have actually settled in a safe third country. But the Trump administration policy doesn't say anything about whether individual Central American asylum-seekers could have settled in Mexico, or whether they have. It simply says that if they haven't sought and been denied refuge somewhere, they can't apply.

After the Trump administration issued the regulation in July, a federal district court in California blocked it from going into effect nationwide. The judge relied partly on the apparent inconsistency of the new rule with federal immigration law. He added that the government was not authorized to create a rule making such significant changes to immigration policy without first going through the process of notice and comment required by the Administrative Procedure Act. And for good measure, he held that the government had failed to provide a rational explanation for its decision, rendering it arbitrary and capricious, another violation of the Administrative Procedure Act.

The U.S. Court of Appeals for the Ninth Circuit left the judge's ruling in place, but narrowed the judge's temporary block on the regulation from the whole country to just the Ninth Circuit, pending its own ruling. The judge subsequently reissued his ban nationwide on the theory that he had been given new facts.

In the good old days, it was extremely unusual for the Supreme Court to reverse an appellate court's decision to stop a rule or law from going into effect while it considered its legality or constitutionality. During the Trump administration, however, it has become increasingly common for the Supreme Court to reverse such temporary bans on a rule or law going into effect.

In her dissent, Sotomayor bemoaned the new frequency of Supreme Court intervention, and argued that the government had not met the high burden necessary to overcome the lower court's temporary block on the policy.

But the truth is that there is an emerging new normal with respect to lower courts blocking executive action nationwide and the Supreme Court saying they can't.

Given that new normal, Breyer and Kagan were taking a calculated gamble by declining to join the dissent. As the case makes its way back to the Supreme Court, they can be expected to tell their colleagues - which really means the swing voter, Chief Justice John Roberts - that they are keeping an open mind. The strong implication is that the other justices should also keep an open mind about the ultimate question of the rule's legality.

Had Breyer and Kagan joined the dissent, that would presumably have created a 5-4 split at this early stage, with Roberts in the majority. That might have made it harder for him to flip to the other side when the case is ultimately argued. By declining to dissent now, Breyer and Kagan are giving Roberts cover to go the other way when the case comes before the court.

I would predict with a high degree of confidence that the ultimate Supreme Court ruling on this case will go 5 to 4. But which way the five will go still remains uncertain.

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Feldman is a Bloomberg Opinion columnist. He is a professor of law at Harvard University and was a clerk to U.S. Supreme Court Justice David Souter. His books include "The Three Lives of James Madison: Genius, Partisan, President."