What would it take for Donald Trump to rip up NAFTA?

Presumptive Republican presidential nominee Donald Trump,not known for mincing his words, made no bones about his views on NAFTA in a speech on Tuesday. It is "the worst trade deal in history,"the real-estate mogul said.

A Trump White Housewould tell itsNAFTApartnersthat is, Canada and Mexicothat the U.Swants to immediately renegotiate the terms of that agreement to get a better deal for Americanworkers.

"And I don't mean just a little bit better, I mean a lotbetter," said Trump.

If the partners couldn'tcome to more favourable terms, Trumpsays he would scrapthe agreement entirely.

• Donald Trump says he would reconsider NAFTA, opt out of TPP
• Barack Obama goes on 'rant' against Trump-style 'populism'
• NAFTA 'a disaster' and I'll renegotiate, says Donald Trump

Specifically, Trump said he would submit notice under Article 2205 of the agreement that America intends to withdraw from the deal.That article states that"aParty may withdraw from this Agreement six months after it provides written notice of withdrawal to the other Parties."

Such warnings aren't exactly new toAmerican politics. Both Hillary Clinton andBarackObamamade similar threatsin 2008, when they were competing forthe Democratic presidential nomination.

Butwould a PresidentTrump have the power to just tear upthe agreement?

The answer: It's unclear.

'The simplest deal to kill'

"It's the simplest deal to kill," saysBarry Appleton, a Toronto-basedlawyer whospecializesin international trade and investment law."TheNAFTAcan be abrogated after six months notice. Period."

And it is the presidentwho would have that authority, he says.

"[Trump]can rip up the deal. He can say to Canada,'You're fired.' The written notice doesn'thave tobe an act of Congress."

• Only 1 in 4supportNAFTAahead of 'Three Amigos' meeting
• How a Donald Trump presidency could affect Canada

There is ample precedent for U.S. presidents unilaterally withdrawing from treaty obligations, saysDonald Abelson, a political science professor at Western University and director of the Canada-U.S. Institute. Former U.S. president George W. Bush, for example, withdrew from the Anti-Ballistic Missile Treaty.

"My understanding is that [Article 2205] is a standard clause which allows their president to withdrawtheir country from the obligations that they were previouslycommitted to."

...Or it may require Congress

Lawrence Herman, an international trade lawyer based in Toronto, disagrees;he believes Congress would need to sign off as well."It's not in the purview of the executive branch."

The murkiness overwho has the power to kill NAFTA stemsin partfrom thedebate over the powers of the American president to make or break treaties, as well as questions aboutwhether NAFTA counts as a treaty or executive agreement.

According toToronto-based international trade lawyer Mark Warner, while a President TrumpcouldnotifyCanadaand Mexico of America's intention to withdrawfromNAFTA, leavingwould require Congress tochangesome of the underlying elements of the agreement.

"And I think it would be a mess,"he say."What [would that mean]in terms of the statutes? Nobody really knows."

MichaelDorf, a constitutional law professor at Cornell University, says it's generally understood that in U.S international law, the president has the authority tounilaterally terminate an agreement.

But that's complicated by the fact thatwhileNAFTAitself was signed by the president, it was Congress that enacted legislation to implement the deal (theNAFTAImplementation Act),and thatstatutes can only be repealed by Congress.

To summarize: Trump could theoretically terminate American obligationsto Canada and Mexico under NAFTA, but it is possible that would rendertheNAFTAImplementationAct invalid, since it wouldn't be implementing anything any longer.

Alternately,it could "continue to have a life on its own, almost as a zombie," Dorf says.If that was the case, then at least some of NAFTA'sprovisions might stay in effect.

An even briefer summary of the situation, according to Dorf:"The answer is unclear."