As soon as this week, the Supreme Court could weigh in on a fraught battle over whether many victims of persecution may seek asylum in the United States — or whether the Trump administration can effectively tell them go back to Mexico.

Last week, the last round of briefs were filed on a stay request involving the Trump administration’s rule, announced in July, that would remake American asylum policy at the Southern border. In the words of a federal court, the new rule would “deny asylum to almost anyone entering the United States at the southern border if he or she did not first apply for asylum in Mexico or another third country.” The same court blocked the rule just days after it was announced, in a case called East Bay Sanctuary Covenant v. Barr.

The Trump administration wants its rule reinstated. So, in what’s become a familiar practice when lower courts suspend this administration’s legally dubious policies, it asked the Supreme Court to stay the lower court’s decision in late August. Because the briefing is complete in this case, the Supreme Court could rule on it at any time — and will likely do so soon.

It’s the latest legal fight involving familiar players: a president eager to push hard-line immigration policies, an administration willing to read the law aggressively to advance those policies, a lower court judge who reads the law less permissively, and a Supreme Court dominated by conservative justices that Trump’s come to view as his ideological allies.

But this case has a twist. The legal theory advanced by the Trump administration in East Bay — the theory that the administration has sweeping authority to limit who may seek asylum — is in tension with a broader project that enjoys the enthusiastic support of the Supreme Court’s most conservative members, diminishing the power of the executive branch to shape policy without going through Congress. Indeed, Trump’s arguments are hard to square with an opinion penned by Justice Neil Gorsuch, the president’s first appointee to the Supreme Court.

East Bay, in other words, provides an early test of how a core conservative project will shake out, and whether this Court is willing to apply the strict limits it appears eager to impose on agencies such as the Environmental Protection Agency to policymakers who advance conservative goals. What’s at stake in East Bay, in other words, is whether the Court’s conservative majority will stick to its stated principles — or whether it only applies those principles selectively to undermine liberal policies.

What is the asylum ban?

The rule at issue in East Bay seeks to address the influx of migrants traveling from Central America to the United States, often crossing the length of Mexico in the process. In the last year, tens of thousands of migrants from Guatemala, Honduras, and El Salvador arrived at the US-Mexico border, often after fleeing violence in their home nations.

Under federal law, any foreign national who “who is physically present in the United States or who arrives in the United States” may seek asylum in this country, although the law does recognize a few exceptions to this general rule. To receive asylum, a foreign national generally must show that that they faced persecution, or that they have a “well-founded fear” of persecution, on the basis of race, religion, nationality, membership in a “particular social group,” or because of their political views.

The Trump administration’s rule, however, would place a sweeping limit on who can seek asylum within the United States. Under this rule, almost any foreign national “who enters, attempts to enter, or arrives in the United States across the southern land border on or after July 16, 2019, after transiting through at least one country outside the alien’s country of citizenship, nationality, or last lawful habitual residence en route to the United States, shall be found ineligible for asylum.” Thus, if an asylum seeker crossed through Mexico to get to the United States, they are out of luck.

This categorical bar on asylum does contain three exceptions. Most importantly, it allows migrants to seek asylum in this country if they “applied for protection from persecution” in one of the nations they traveled through, but only if the foreign national “received a final judgment denying the alien protection in such country.”

This new rule would significantly expand the universe of immigrants who are ineligible for asylum. By law, two narrow categories of immigrants are denied asylum if their journey took them through another nation: those who can be removed to a “safe third country” outside of the United States, and those that are firmly resettled in another country prior to arriving in the United States.”

But the “safe third country” exemption only applies to countries that the United States has a formal agreement with — we currently only have one with Canada — and it is quite a stretch to say that someone who merely passed through Mexico on the way to the United States is “firmly resettled” in Mexico.

Nevertheless, the Trump administration claims that it has extensive authority to create new categories of immigrants who may not seek asylum without having to go through Congress. In its application for a stay of the lower court’s decision, the administration claims that it has a broad power to “establish categorical ‘limitations and conditions’ on asylum eligibility, beyond those already set out in the statute,” and that this power includes the ability to lock most Central American migrants out of the asylum process.

Can they do that?

The question that looms over this issue: Can the administration change asylum policy the way that Trump is proposing without going through Congress? The short answer is that it all depends on just how much unchecked power the Supreme Court is willing to hand to the executive branch.

The Trump administration points to a provision of federal law allowing the attorney general to “establish additional limitations and conditions, consistent with this section, under which an alien shall be ineligible for asylum.” Though the asylum statute only lists a few, narrow exceptions to the broad rule that any foreign national may apply for asylum, the Trump administration claims that those limits “merely establish minimum statutory requirements” and “do not foreclose the Executive from imposing additional, more stringent requirements.”

The parties challenging the asylum ban disagree. “Congress went out of its way to underscore that only bars ‘consistent with’ the entirety of the asylum laws ... were permitted,” they write in their brief asking the Supreme Court not to grant a stay — and it is not consistent with a statute that creates specific, narrow limitations on who can seek asylum to allow the administration to create expansive new limits.

More significantly, the challengers also argue that giving the executive branch such sweeping authority to define the scope of asylum law “flouts bedrock principles of separation of powers and administrative law.”

That’s the very sort of argument that could drive a wedge between Trump and his allies on the Supreme Court.

Last June, in Gundy v. United States, the justices considered a federal law that appeared to give the attorney general very broad authority to decide whether certain sex offenders need to register with the government after they have otherwise served their sentences. The Supreme Court resolved the case in a messy 4-1-3 split that upheld the law, with Obama-appointed Justice Elena Kagan writing for her liberal colleagues that the statute at issue in Gundy “easily passes constitutional muster.”

Justice Samuel Alito, a very conservative justice and the Court’s most reliable vote for prosecutors, wrote an unusual opinion saying that he would support placing new limits on Congress’s power to delegate policymaking to the executive branch — but not in this case. Justice Brett Kavanaugh, a conservative Trump appointee, did not participate in the case because he was not a yet a member of the Court when Gundy was argued.

That means that, with Kavanaugh benched and Alito writing a one-off, good-for-this-ride-only opinion, the Court’s Republican majority was two votes shy of the five it needed to limit policymaking by federal agencies.

But if you want to know what the future of federal administrative law is likely to look like in just a few years, you should start with Justice Neil Gorsuch’s dissent in Gundy.

Gorsuch’s Gundy opinion is a major milestone for an effort spearheaded by conservative lawyers and academics — and popularized among these scholars and advocates by the conservative Federalist Society — that seeks to revive a long defunct doctrine known as “nondelegation.” Many federal laws lay out a broad policy goal — such as ensuring that power plants use the cleanest, reasonably available technology, or preventing health providers from engaging in certain forms of discrimination — but instruct agencies to write regulations that implement the details of these policies and that can be updated as new developments require such updates.

Indeed, this power to delegate regulatory authority to the executive branch forms the backbone of both the Clean Air Act and the Clean Water Act. It would be difficult, if not impossible, to sustain a modern environmental protection regime if the EPA — or, at least, some other agency with significant expertise in environmental policy — could not be given the power to update clean technology regulations as that technology improves.

Nevertheless, the nondelegation doctrine would constrain — perhaps quite considerably — Congress’s ability to delegate power to a federal agency. As Gorsuch wrote in his Gundy dissent, executive agencies should not have “unbounded policy choices.” Rather, a law instructing the executive to implement a particular policy through regulation typically must be “sufficiently definite and precise to enable Congress, the courts, and the public to ascertain’ whether Congress’s guidance has been followed.”

Which brings us back to the asylum ban.

Recall that the Trump administration relies on a vague provision of federal law allowing it to “establish additional limitations and conditions, consistent with this section, under which an alien shall be ineligible for asylum.” Try to find a “definite and precise” instruction in that statutory language that can be used to determine “whether Congress’s guidance has been followed.”

Gorsuch, in other words, suggested in Gundy that Congress must clearly and narrowly define the scope of the power it delegates to a federal agency, or else the delegation is void. Yet, while the challenger’s interpretation of the statute may pass Gorsuch’s test, the Trump administration’s interpretation would give them virtually boundless power to create new asylum exemptions.

Is there an “immigration exception” to the nondelegation doctrine?

It’s worth noting that Gorsuch’s Gundy opinion does contain some language that could allow him to distinguish immigration from the environmental and other regulations that the nondelegation doctrine would dismantle. Gorsuch writes that “when a congressional statute confers wide discretion to the executive, no separation-of-powers problem may arise if ‘the discretion is to be exercised over matters already within the scope of executive power.’” Historically, the Supreme Court’s given the executive broad deference on matters of foreign policy and national security, and the Court’s decisions also recognize that immigration is intertwined with America’s foreign policy.

But the Court’s conservative majority also cannot have it both ways on immigration. In 2016, the Supreme Court split 4-4 on whether President Obama could implement his Deferred Action for Parents of Americans and Lawful Permanent Residents (“DAPA”) program, which would have liberalized American immigration policy beyond actions already taken for young immigrants. Though the Court did not reveal how each justice voted in this case, the justices’ comments at oral argument strongly suggest that they split along party lines.

The DAPA case was not a nondelegation case, but it closely resembled East Bay in that it turned on whether immigration statutes that can be read to give the president wide discretion over immigration policy should be read broadly or narrowly.

Gorsuch was not on the Court when it decided the DAPA case, so maybe he’ll see that case differently than his fellow conservative justices — although no smart lawyer would bet on such an outcome. But, in any event, if Gorsuch is willing to create an immigration exception to the strict limits he’d place on federal agencies, that exception should apply to liberal and conservative policies alike.

More broadly, East Bay is a test of whether Gorsuch and the other Republican justices who signed onto Gorsuch’s nondelegation project are willing to apply their principles neutrally when they cut against conservative goals. If they are, that at least means that the Supreme Court remains a court of law where the same rules apply to Democrats and Republicans alike.

And if they aren’t, that should send a chill down the spine of any American who cares about liberal democracy.