A growing number of countries are criticizing and issuing warnings about the recent legalization of marijuana in Canada.

The situation is causing alarm for travellers, and it turns out the penalties could go both ways.

Recreational weed has been legal in Canada for a week, but if international border guards ask, admitting to cannabis consumption could lead to trouble.

"Once you're across the American border and they find out you smoke weed, it's a lifetime ban, and that makes it difficult because a lot of travel goes through the United States," one person told CTV News.

And it's not just U.S. travel. Tourists coming to Canada could face even more issues.

The Russian embassy isn't mincing words about legalization, accusing Canada on Twitter of "weakening the international legal drug control framework."

South Korea went even further, warning its citizens not to smoke up while on holiday: "Even if you are in a cannabis legalization area, you will be penalized for committing a criminal offence."

Japan warns tourists they should observe Japanese laws even while travelling.

Businesses cashing in on bud are warning their customers.

"I feel like one of our obligations as a country where it is legal is to tell tourists, to tell visitors what the rules are around cannabis here," said Tristin Slade of High Definition Tours.

One associate professor of law says even Canadians visiting those countries could be charged over consuming cannabis in the past.

"What is legal in Canada may not be permissible in any way, shape or form, and may be punishable in that other legal system," UBC's Elizabeth Edinger said.

But those considering lying about past use should be wary.

"Even if they're very good liars, if the truth becomes known they could be in more trouble for lying and attempting to cover up the truth than if they had just told the truth," Edinger said.

With a report from CTV Vancouver's Breanna Karstens-Smith