President Trump sparked a frantic response from advocates and scholars this week when he announced that he could terminate birthright citizenship for children of undocumented parents with an executive order. The bulk of that response has focused on the question of what the Constitution means with respect to birthright citizenship. The other question raised by Trump’s assertion is structural: who gets to decide what the Constitution means with respect to birthright citizenship?

These questions are intimately related: Who decides (the President or Congress) can have implications for what is decided (to end or continue birthright citizenship). But they have not generally been treated that way. Instead, the first question has dominated headlines and coverage, with the other question—who decides—playing second fiddle. Moreover, to the extent the second question has been covered (e.g., here, here, and here), little or no account has been made for how the rules of constitutional engagement are different in the field of immigration, particularly in light of two recent decisions by the Supreme Court: Trump v. Hawaii (2018) and Sessions v. Morales-Santana (2017).

Our goal here is to connect these dots, with an emphasis on whether the President (as opposed to Congress) could lawfully decide whether children born to undocumented parents in the United States are citizens at birth. We join those who believe he cannot, but partly for different reasons, and with sensitivity to the oft-overlooked wildcard of immigration exceptionalism.

The Substantive Question

Jus soli birthright citizenship is codified in federal statute and enshrined in the Fourteenth Amendment. The relevant constitutional clause states that “All persons born . . . in the United States, and subject to the jurisdiction thereof, are citizens of the United States. . . .” And the relevant statute, 8 U.S.C. § 1401(a), mirrors that language. For over a hundred years, all three branches of government, every state, the general public, and the vast majority of legal scholars have operated under the shared belief that the children of undocumented immigrants born in the United States are “subject to the jurisdiction thereof,” and thus citizens at birth.

The Other Question

Even if that collective view is mistaken, as Trump’s supporters now claim, it remains the law of the land. For that reason, most scholars believe that denying birthright citizenship to the children of undocumented immigrants would require a constitutional amendment. That is a near impossibility in today’s political climate. Short of an amendment, a distinct minority view posits that Congress may lawfully interpret the Fourteenth Amendment’s Citizenship Clause to exclude children of undocumented immigrants. Practically speaking, a statutory alteration would be far easier than a constitutional amendment, which is precisely why some suggest it as a possibility. Although easier, it is far from easy. A bill to eliminate birthright citizenship for the children of undocumented immigrants is unlikely to survive the legislative gauntlet. In recent decades, several attempts were made and fell flat each time.

But, more to the point, even among the few who think Congress can reshape the meaning of the Citizenship Clause, it is still Congress—not the president—that gets to decide who can be a citizen.

The current statute on the books, as intended by Congress and long implemented by the Executive branch, confers birthright citizenship to the children of undocumented immigrants. Thus, even assuming arguendo that the statute confers more rights than the Constitution requires, the President cannot override or nullify that statute with an executive order.

President Trump’s assertion to the contrary is at the very fringe of the fringe of legal possibility.

Perhaps for that reason, many commentators have dismissed President Trump’s claim as a political bluff, given its proximity to the mid-term elections. Time will tell. Yet we think it’s a mistake to not take his claim seriously.

It would be rather easy for him to sign an executive order, and not nearly as politically risky as many assume (especially if that assumption is based on conventional political calculations). Trump has proven more than willing to charge into thorny legal territory. Thus, rather than summarily denounce Trump’s claim as political posturing, advocates should prepare for the possibility that an executive order on birthright citizenship may indeed be forthcoming.

If his handling of the travel ban is any indication, Trump is unabashed in his willingness to take legally-suspect action to the delight of his base, blaming any ensuing legal losses on others. As is all too plain, “immigration blame” is a plank in Trump’s agenda. Migrants carry the brunt of it. But any who stand in Trump’s way are also blamed—including judges. Consider, in this light, Trump’s tweet when his first executive order banning Muslims was enjoined: “Just cannot believe a judge would put our country in such peril. If something happens blame him and court system. People pouring in. Bad!” On the flipside, while the threat of being blamed may deter other political figures from risky political action, Trump’s threshold is much higher than the norm. [Ed. note — For more on how blame shapes the politics, policies, and structures of the U.S. immigration system, read Rubenstein’s article, “Immigration Blame,” published last month in Fordham L. Rev.]

Given the political possibility of unilateral presidential action, it is also a mistake to brusquely dismiss its legal potential. If Trump issues an executive order attempting to end birthright citizenship for the children of undocumented immigrants, he will be betting on the same legal principles that helped him prevail in Trump v. Hawaii.

By proclaiming the authority to act alone, President Trump is essentially saying “We Can’t Wait” for Congress to amend its own citizenship statute. Never mind that this is precisely what Republicans excoriated President Obama for when he announced, in words and actions, that “We Can’t Wait” for Congress to fix the broken immigration system. More than ironic, presidential self-help should be met with extreme skepticism, regardless of party or ideology. The notion that a president is justified to go-it-alone, without Congress, will always appeal to ambitious presidents and be dangerous for that very reason.

But here’s the catch: normal constitutional rules do not always apply to immigration. Thus, even if presidents normally cannot alter congressional statutes or flout constitutional rights, more than a century of jurisprudence demonstrates that immigration law is sometimes exceptional. The Supreme Court’s decision last term in Trump v. Hawaii is a case in point. Upholding the travel ban, the Court stressed that “[t]he case before us differs in numerous respects from the conventional Establishment Clause claim.” In other words, mainstream constitutional norms did not apply. Rather, the Court explained, ” [f]or more than a century, [it] had recognized that the admission and exclusion of foreign nationals is a ‘fundamental sovereign attribute exercised by the Government’s political departments largely immune from judicial control.'”

Now again, immigration exceptionalism may be the only possible legal justification if Trump does issue the birthright citizenship executive order he has described. For reasons explained below, we don’t think it would be a winning claim. But that is a reason to take it head on. Whatever one’s views are about immigration exceptionalism, ignoring it is not the right approach.

New Relevance for Morales-Santana?

Two terms ago, in Sessions v. Morales-Santana, the Supreme Court announced a key limit to immigration exceptionalism, and the so-called plenary power doctrine that supports it. In striking down a federal citizenship statute that discriminated against parents on gender grounds, the Court applied mainstream equal-protection doctrine, and explicitly drew a line between immigration decisions by the political branches (to which the plenary power doctrine generally applies) and citizenship decisions (to which the doctrine does not). Put otherwise, the plenary power cases that the Court seized upon in Trump v. Hawaii—which involve the admission and expulsion of non-citizens—are inapplicable to citizenship cases.

When Morales-Santana was first decided, and still today, it received a mixed reception from immigrant advocates and constitutional scholars. On the one hand, the decision seemed to reify the plenary power doctrine in immigration cases. On the other hand, Morales-Santana treated the subject of citizenship as an enclave in which the plenary power doctrine does not apply. Depending on perspective, that trade-off may or may not be worth celebrating. But with birthright citizenship on the national agenda, the citizenship safe-harbor from immigration exceptionalism takes on new, heretofore overlooked, significance. In concrete terms, it means that President Trump may have special latitude to shape our nation’s immigration policies yet remain subject to the normal constitutional restraints on questions involving citizenship.

Although Morales-Santana involved judicial review of a congressional statute, there is no reason to suppose that presidents enjoy any more constitutional leeway than Congress. Indeed, the opposite is true: case law suggests that presidents are entitled, at most, to the same deference generally afforded to Congress in immigration matters. By extension, because the plenary power doctrine does not apply to Congress’s citizenship decisions, it clearly does not apply to President Trump’s citizenship decisions either.

To say that Trump will not enjoy special solicitude over questions of citizenship does not eliminate, much less resolve, the substantive question about the proper interpretation of the Citizenship Clause (for the widely-held majority view, see here and here; for the distinctly minority view, see here and here). What Morales-Santana does entail, however, is something quite different than what ensued in Trump v. Hawaii. Both procedurally and substantively, an executive order to limit birthright citizenship will be met with scrutinous judicial review and will almost certainly fail for that reason.

Gillian Chadwick is an Associate Professor of Law at Washburn University School of Law where she teaches Immigration and Law Clinic. Professor Chadwick is also Associate Director of the Children and Family Law Center. David S. Rubenstein is a Professor of Law at Washburn University School of Law. This post first appeared on the Washburn Law Journal blog here.