Editor's note, March 27, 2015: We have published a new story on this topic since Cruz announced he will run for president in 2016. Read our latest report.

Can Ted Cruz run for president if he was born in Canada?

The Republican senator from Texas says he can. And just to be sure, he’s taking the extra step of renouncing the Canadian citizenship he says he didn’t even know he had.

Cruz -- full name: Rafael Edward Cruz --was born in Canada in 1970 because his father was working for the oil industry there. The senator’s recently released birth certificate shows his mother was born in Delaware and his father was born in Cuba. The Cruz family left Canada a few years later. Cruz grew up in Texas and graduated from high school there, later attending Princeton University and Harvard Law School.

By virtue of his American-born mother, Cruz, 42, considers himself a natural born citizen and eligible to run for president.

So is he eligible? The vast majority of legal thought and arguments indicate he is.

Is there the tiniest sliver of uncertainty? Yes, there’s that, too.

Constitutional requirements

The Constitution says any candidate for president must be 35 years of age, a resident within the United States for 14 years and a "natural born citizen."

We’ve looked at the question of natural born citizenship before. Back in 2008, people raised questions about the "natural born" citizenship status of both major party candidates.

We’ve fact-checked several statements about President Barack Obama’s place of birth and his birth certificate . Obama was born in Honolulu, Hawaii, and his mother was a U.S. citizen. His father was Kenyan.

We also looked at the case of John McCain, who was born in the Panama Canal Zone because his American father served in the military. McCain, the 2008 GOP nominee, saw his standing briefly challenged in court.

Interestingly, both of McCain’s potential Democratic opponents -- Obama and then-Sen. Hillary Clinton -- co-sponsored a Senate measure to settle McCain’s eligibility. The April 2008 resolution said, "John Sidney McCain, III, is a 'natural born Citizen' under Article II, Section 1, of the Constitution of the United States."

Defining "natural born"

So what is a "natural born" citizen? The Constitution doesn’t specifically say.

In 2008, we reviewed research and polled several legal experts. The consensus was that someone is a "natural born" citizen if they have citizenship at birth and don’t have to go through a naturalization process to become a citizen.

If that’s the definition, then Cruz is a natural born citizen by being born to an American mother and having her citizenship at birth. (This same logic would apply to Obama, even if he were born in another country, which he wasn’t.)

The Congressional Research Service published a report on the issue after the 2008 election; the agency is tasked with providing authoritative research to all members of Congress. It, too, supported the thinking that "natural born" citizenship means citizenship held "at birth."

But the Supreme Court -- the ultimate arbiter of constitutional questions -- has never ruled on the matter. And that means a note of uncertainty remains.

Sarah H. Duggin, a professor of law at Catholic University, has written about and studied the issue extensively. She told us in 2008 that the question of natural born citizenship is "one of the most deceptively simple, complex issues."

We reached her again this week to ask about Cruz’s eligibility. "It would be reasonable to interpret the Constitution’s natural born citizenship provision to include children born abroad to U.S. citizens, including Senator Cruz, for a number of reasons," she said.

But is it 100 percent sure?

"Unfortunately, we cannot say for sure without either a definitive Supreme Court ruling, or an amendment to clarify the Constitution."