BOSTON — Two legal scholars squared off in a public debate on Friday to settle whether Republican Ted Cruz is eligible to become president. Spoiler alert: They didn't settle it.

But the debate at Harvard Law School underscored that conflicting interpretations of the U.S. Constitution can produce different answers. The question has been in the national spotlight since Republican rival Donald Trump suggested that Cruz, who was born in Canada to an American mother, isn't legally qualified to be president.

Much of the debate weighed whether Cruz is a natural born citizen, a requirement under the Constitution to become president that the document never defines.

Harvard professor Larry Tribe argued that, based on legal principles from the country's early history, only those born on U.S. soil can be considered natural born citizens. Granting that status to Cruz, then, "is at odds with the text, the structure and the founding history of the Constitution," said Tribe, who once taught Cruz as a Harvard law student.

But by the time Cruz was born, newer laws would have made him a U.S. citizen because his mother already had that status, said Jack Balkin, a constitutional law professor at Yale Law School.

Balkin's argument is hinged on the idea that the newer rules, created by Congress, changed the definition of a natural born citizen. Tribe said Congress doesn't have that right.


Cruz has previously said it's already settled that he's legally eligible, and he called Tribe a "liberal left-wing judicial activist" who supports Democrat Hillary Clinton. On Friday, Tribe took a few jabs at his former student, but added that Cruz "was a fun student to have; I enjoyed jousting with him."

Tribe said he isn't dismissing the possibility that Cruz could be eligible for the White House, but he insisted that it's still an open question.

"In no possible sense has the issue been settled, either by the Supreme Court or by political processes or by popular consensus," Tribe said.

Other scholars have recently taken sides on the question while presidential candidates stump across the country. Cruz and other candidates were in New Hampshire Friday ahead of Tuesday's first-in-the-nation primary election.

For now, the debate is mostly academic — it hasn't been taken up by the judicial system. But both professors said it has the potential to end up before the Supreme Court. If a state election official leaves Cruz off the ballot because of the citizenship question, for example, they said Cruz could take it to the Supreme Court.

But if that happens, there would be a twist, Tribe said. The Supreme Court's liberal wing would be more likely to take a flexible approach to the Constitution and side with Cruz, Tribe said. "Conservatives on the Supreme Court," he added, "would have a harder time finding him eligible."