At the very least, neither the coronavirus crisis nor the supposed wage effects can justify a categorical ban that applies to virtually all immigrants seeking permanent residency, regardless of their circumstances and regardless of whether the individuals in question pose any kind of public-health or economic risk.

Trump’s new immigration restriction is also a dangerous constitutional-power grab. Like Trump’s earlier, more limited “travel bans,” the new policy relies on 8 U.S.C. Section 1182(f), which gives the president the power to bar entry into the U.S. by any foreign national he deems “detrimental to the interests of the United States.” In Trump v. Hawaii, the 2018 Supreme Court ruling that upheld Trump’s travel ban targeting several Muslim-majority nations, Chief Justice John Roberts’s majority opinion interpreted this language as giving the president virtually unconstrained power to exclude any foreigners for any reason, so long as he claims—even without evidence—that their entry might harm American “interests.”

Trump v. Hawaii did not consider the possibility that this view of Section 1182 violates the “nondelegation” doctrine: the principle that Congress cannot delegate sweeping lawmaking power to the executive. In last year’s ruling in Gundy v. United States, both liberal and conservative justices indicated the real limits on that delegation of power. In a dissenting opinion joined by two other conservatives, Justice Neil Gorsuch emphasized that the Constitution does not allow the president to exercise “the power to adopt generally applicable rules of conduct governing future actions by private persons.” Only Congress may do that. Justice Elena Kagan’s plurality opinion for the Court held that Congress may not give the president “‘unguided’ and ‘unchecked’ authority” to determine the scope of a law, especially when violations carry criminal penalties. Trump’s use of Section 1182 to impose a sweeping ban on immigration pretty obviously makes “generally applicable rules of conduct” for private parties—many millions of them. The recent extension and expansion of the policy applies these rules to even more people. Just as clearly, the idea that the president can exclude any potential immigrant for any reason, subject to the imposition of criminal penalties for violators, is a case of “‘unguided’ and ‘unchecked’ authority,” if anything is.

If we are serious about nondelegation limits on presidential power—as conservatives, in particular, claim we should be—then the courts must either strike down Section 1182(f) or rethink the broad interpretation of the law adopted in Trump v. Hawaii. For its part, Congress should consider repealing Section 1182, or at least imposing tighter limits on its scope. Unless and until that happens, Trump’s green-card and employment-visa bans will remain dangerous precedents for future presidents.