Marijuana becomes legal in Canada on Oct. 17. our neighbours to the south?

It’s a change that apparently is not sitting especially well well with our neighbours to the south.

According to a U.S. Customs and Border Patrol senior official, those who work in the cannabis industry, those who invest in the cannabis industry, and anybody who tells a U.S. customs agent that he or she has smoked pot–ever–risk a lifetime ban on travel to the U.S.

Cars from Canada line up to cross into the U.S. at Blaine, Wash. A top U.S. official nows says past use of cannabis could lead to Canadian travellers being barred from entering the U.S. (Elaine Thompson/AP Photo)

“Canadians are going to let their guard down and think what’s the problem,” says Todd Owen, executive assistant director for the Office of Field Operations for U.S. Customs and Border Protection Agency.

Thousands of Canadians have invested in the cannabis companies, which are publicly traded on the Toronto Stock Exchange.

A lot of people will be working at those companies and it’s a very safe bet that tens of thousands Canadians have smoked pot.

So what to do when you want to cross the border?

“Our officers are not going to be asking whether they have used marijuana, but if other questions lead there–or there is the smell coming from the car, they might ask,” Owen told the online magazine Politico.

Owen says if a traveller is asked about past use use, he shouldn’t lie.

“If you lie about it, that’s fraud and misrepresentation, which carries a lifetime ban,” he says.

Should a traveller admit to past use, he will be found to be “inadmissible” to the U.S.

He will then be giving the opportunity to “voluntary withdraw” from the border–or face “expedited removal.”

No matter the traveller’s choice, it all goes on the record and that traveller will not be allowed to return to the U.S unless he applies for a waiver to strike the lifetime ban.

Prime Minister Justin Trudeau said Tuesday Canada is working with U.S. officials try to make sure travel between the two countries is not disrupted. (Darryl Dyck/Canadian Press)

That process costs US$585,  takes several months to work through, and.U.S. Customs and Border Patrol gets the final say.

Owen’s comments confirm anecdotal evidence over the past year that the tough measures were coming.

It remains unclear what Canada can do.

Prime Minister Justin Trudeau downplayed the matter on Tuesday, though he has said publicly he has smoked pot.

“Every country has the right to judge who gets to come into their borders or not,” he said.

“I wouldn’t presume to have any other country tell me how or who we can let into Canada, and I certainly won’t work to assume to impress upon the U.S. who they have to let in or not.

“But there is no question that we are working with U.S. officials; they have legalized marijuana in a number of their states, and we’re trying to make sure that travel between our two countries (is) not disrupted.”