Could Donald Trump be right? Could Ted Cruz be ineligible for the Presidency? What exactly is a “natural born citizen,” anyway?

In our highly mobile nation of immigrants, the last question is one we are confronting with growing frequency. The Constitution (article II, section 1, clause 5) says our President has to be one, and each election cycle we seem to be surprised anew at the knotty, anachronistic, inequitable repercussions of the restriction.

The scholars who are most deeply schooled in the question agree that the answer is anything but simple.

In modern times the “natural born citizen” issue has arisen with respect to John McCain in 2008 (born on a Navy air base in the Panama Canal Zone), Mitt Romney’s father, George, in 1968 (Mexico), and Barry Goldwater in 1964 (Arizona territory prior to statehood); hypothetically with respect to potential candidates like former California governor Arnold Schwarzenegger (Germany) and former Michigan governor Jennifer Granholm (Canada); and contingently vis-à-vis statesmen in the line of Presidential succession, like former secretaries of state Madeline Albright (Czechoslovakia) and Henry Kissinger (Germany). (Imagine a crisis in which President became incapacitated and, due to unsettled, Constitutional obscurities, we don’t even know who’s in charge.)

Cruz was born in Canada in December 1970 to a U.S. citizen mother and a Cuban-born, Canadian citizen father. He was himself a dual citizen until 2014, when he relinquished his Canadian citizenship.

Constitutional scholars have served up two main contenders for what “natural born citizen” might mean. First, it could refer to people who were actually born in this country, with only a very few exceptions that were established by the British common law (i.e., judge-made precedents) as of 1787 and 1788, when our Constitution was drafted and ratified.

Proponents of this view then disagree among themselves over whether the stingy British common law definition should also be widened to include certain eighteenth century Parliamentary statutes also in effect at the time.

Professor Mary Brigid McManamon, of Widener University Delaware Law School, may be the leading proponent of the first school of thought, see here and here, while professor Sarah Helene Duggin, of Catholic University, has reached some similar conclusions. McManamon cites writings suggesting that no less an authority than James Madison was also among those who understood the clause in this fashion.

Under these interpretations, Cruz seems to be excluded, for reasons we’ll discuss shortly.

Then there’s the more permissive alternative. “Natural born citizen” might simply refer to anyone who, thanks to whatever immigration laws happened to be in effect at the time of his or her birth, was automatically considered a U.S. citizen without having to go through the rigamarole of naturalization. If this is the correct interpretation, the Constitution actually provides no single, immutable, citizenship requirement applicable to all presidential hopefuls. Instead, it delegates to each Congress the power to define and redefine precisely which people it thinks should be encompassed by the phrase “natural born citizen.”

This is the interpretation that has been advocated by, among others, former solicitor generals Paul Clement and Ted Olson; former acting solicitor general Neal Katyal; University of Baltimore law professor Garrett Epps; Yale law’s Akhil Reed Amar and Jack Balkin; Harvard’s Cass Sunstein; a Congressional Research Service monograph produced in 2011; and—after wrenching internal debate and a deep scholastic dive—University of San Diego law professor Michael Ramsey.

Under this second approach, McCain, Romney, and Goldwater sail through, and Cruz sneaks in under the wire as well. It’s a close call in Cruz’s case because, oddly enough, his U.S. citizenship hinges on the nooks and crannies of his mother’s resume. According to professor Steven Lubet of Northwestern University , under the laws in effect at the time of Cruz’s birth, a baby born beyond our borders was eligible for automatic U.S. citizenship only so long as at least one of his or her parents had been not only a citizen, but had also been “physically present” in the U.S. for at least 10 years prior to the birth, including five after the age of 14. Cruz’s father, a noncitizen, fails the test, but his mother, born in Delaware and reportedly a graduate of Rice University, appears to meet it. (Lubet tweaks Cruz for once having sought to introduce an amendment to an immigration bill that would have required would-be voters to provide documentary proof of their citizenship. In Cruz’s own case, Lubet argues, that would have required a substantial dossier.)

One problem with this second, more permissive approach to defining “natural born citizen” is that, as professor Ramsay has acknowledged, it seems to render the word “natural” superfluous. If anyone is eligible to whom the law confers citizenship at birth, why didn’t the Framers of the Constitution just say “born citizens”?

Finally, there’s a camp that seems to want to use Cruz’s judicial philosophy against him. Harvard’s Laurence Tribe has suggested that while he personally favors the second approach, more conservative jurists, who advance orthodox “originalist” approaches to constitutional interpretation, ought to find themselves stuck with the first. Since Cruz has pledged to appoint just such originalists to the Supreme Court, Tribe is, in essence, attempting to shove Cruz’s jurisprudence up his—well, strike that. Tribe is accentuating what he sees as an irony in Cruz’s position. Similar sentiments have been expressed by such academicians as Fordham’s Thomas Lee, and Cornell’s Michael Dorf. (Nevertheless, professors Amar and Ramsey have each offered originalist analyses that conclude that Cruz is eligible.)

Cruz, for his part, has preferred not to engage Tribe on his own turf. Instead, he has responded that Tribe is giving him a hard time because Tribe is a “left-wing judicial activist.”

But why does the first school of thought—the one that defines “natural born citizen” in accordance with English common law—pose a problem for Cruz in the first place? Professor McManamon contends that the traditional common law view, reflected, for instance, in Blackstone’s Commentaries, was that a “natural born” British subject was someone born within the realm, with only extremely narrow exceptions (like for the children of British ambassadors). Under this narrow definition, McCain, Romney, Goldwater, and Cruz are all out of luck.

Broadening the definition of “natural born citizen” to encompass the definitions of Parliamentary statutes in effect at the time our Constitution was drafted (and not just the judge-made common law) would permit McCain, Romney, and Goldwater back onto the ballot, but Cruz might still be banished. The acts of Parliament provided that a child born beyond British borders would be treated as “natural born” only if both his parents were citizens, or if at least his father was. Neither of these conditions was true of Cruz.

While it’s may seem plum crazy to exclude Cruz based on such an archaic, paternal rule, that is part of Tribe’s point: If Cruz wants rigid faithfulness to the words of the Constitution as they would have been understood in 1788, he may be hoist on his own petard.

Finally, scholars on both sides of the debate lavish attention on a law enacted by the first U.S. Congress in 1790, although they diametrically disagree about which way it cuts. Since many framers of the Constitution sat in the first Congress, its acts are thought to shed light on what the framers were thinking.

The law says that “children of citizens of the United States” that are born beyond its borders “should be considered as natural-born citizens.” The reference to “natural born citizen” was quickly deleted from the statute in 1795, for unknown reasons, and then the whole law was repealed and replaced with numerous other formulations over the nation’s history. (There was also a paternal proviso in the original statute specifying that “citizenship shall not descend to persons whose fathers have never been resident in the United States.” But Cruz actually would have met this standard. His father, while a non-citizen, had resided in Texas for a period.)

So which side of the debate does this law support? Some say it actually favors the restrictive theory: If, as a constitutional matter, babies born to citizens outside the borders were already considered “natural born citizens,” why would this statute even have been necessary? The more permissive camp, on the other hand, says the law shows that, at the time, everyone understood that Congress was empowered to define what “natural born citizenship” meant, and the first Congress was, therefore, doing just that. But those who favor the more restrictive reading protest that the law did no such thing. It simply specified who had to go through the naturalization process, they contend, and had nothing to do with eligibility to become President, which was subject to an independent, immutable Constitutional standard.

What’s the upshot? First, many more authorities end up favoring the second, more permissive view, so perhaps there is a consensus.

But nothing is truly “settled” until the Supreme Court has ruled on it. Which leads to the final question: Will it ever do so? Several lower courts have ruled that voters don’t have the requisite personal stake—or standing—to raise the issue. (A voter suit relating to Cruz’s candidacy was filed in federal court in Houston last week.)

Candidate Donald Trump has urged Cruz to bring his own declaratory judgment action, seeking clarification of his eligibility. But—as Trump well understands—for Cruz to do that would be politically undermining, since it would validate Trump’s claim that there’s a genuine cloud hanging over the Cruz candidacy—a claim Cruz wants to deny.

Nevertheless, professors Balkin and Duggin have each written that if any elections official ever deprived Cruz of a spot on the ballot, Cruz would certainly have standing to sue.

The next question would be whether the Court would decide the case or abstain on the grounds that the issue was a “political question” to be resolved by the political branches, and not by the judiciary. Professor Amar, for instance, thinks the Court should “butt out, now and forever,” and let Congress decide the question—perhaps when it is exercising its power to count electoral college votes. But, of course, Amar also thought the Court should have stayed out of Bush v. Gore.

Yale’s Balkin believes the Court would decide the case, just as it would if someone mistakenly tried to keep a candidate off the ballot for being under the constitutionally mandated age of 35.

Speaking as a lapsed lawyer—essentially, a layperson—it does seem like a little guidance from the Court would be appreciated in this area.

Though preferably not by a 5-4 vote along political lines.