Sen. Rand PaulRand PaulDestructive 'fat cat' tax law a complete flop. It's time to repeal it. Trump must take action in Macedonia to fix damage done by Obama and Clinton We can put America first by preventing public health disasters MORE (R-Ky.) is calling 2016 White House rival Sen. Ted CruzTed CruzOvernight Defense: Senators go to White House for North Korea briefing | Admiral takes 'hit' for aircraft carrier mixup | Lawmakers urged to beef up US missile defense Senators get North Korea briefing in unusual WH visit Overnight Tech: FCC chief unveils plan for net neutrality rollback | Tech on Trump's sweeping tax plan | Cruz looks to boost space industry MORE (R-Texas) a "natural-born Canadian" and saying the Supreme Court may need to weigh in on his eligibility for the presidency.
"I think without question, everybody would accept that, you know, Cruz is a natural-born Canadian, that he was naturally born there," Paul said in an interview on Fox News on Monday.
The Kentucky senator clarified that he wasn't calling into question Cruz's citizenship, saying that the constitutional requirements for holding executive office are more ambiguous than those for becoming a citizen.
"The only part of the Constitution that says 'natural-born' is with regard to the president. So it appears to be a unique qualification, and most people have interpreted they have to be born in the U.S. until recently.
"I think the Democrats are going to force it to be adjudicated, and I think the Supreme Court is going to have to decide it," he added.
Cruz was born in Canada to an American mother and a Cuban father, leading GOP rival Donald Trump to raise questions about his eligibility for the White House.
Rep. Alan Grayson (D-Fla.) has also vowed to file a lawsuit challenging Cruz's eligibility if the senator and Iowa front-runner wins the GOP nomination.
Cruz made the case for his eligibility for president on Sunday, saying any legal questions had been settled.