CNN  — 

As laws surrounding recreational marijuana change state by state in the United States, Canada has just legalized weed nationwide.

Adults there can now purchase pot and and even grow it in their homes for personal use.

The Canadian Senate bill, which passed in June and just took effect, is clear in how it pertains to Canadian residents. But how does it affect foreign visitors and tourists?

Here are some things to be wary of before you travel north for a smoke or an edible:

The rules are different across cities and provinces

The law legalizing marijuana use is federal, but each Canadian province and state can add laws on top of that.

For example, the province of Alberta has some of the most liberal laws on marijuana use, but Calgary – the biggest city in Alberta – has banned the use of recreational pot in public. Violating the law could mean a $100 ticket. Recreational marijuana use is legal in private places, but landlord and tenant agreements are allowed to forbid cannabis use, the city says.

The rule against public marijuana use is particularly limiting for tourists, who may not have a private location to smoke. Be sure to check province and local laws before planning any marijuana tourism.

You can’t legally leave Canada with weed

Marijuana may be legal in some states in the United States, but it is still prohibited federally. That means it is still illegal to bring marijuana purchased in Canada across the border into the United States.

Yes, even if you are flying into a state where it is legal, such as Colorado.

Vancouver International Airport (YVR) is already taking measures to warn travelers about carrying marijuana across international borders. A sign up at YVR reads: “Crossing international borders with cannabis is illegal,” according to an October 16 Global News article.

This means that even going from, say, Vancouver to Los Angeles International Airport (LAX) is risky – even though LAX recently announced that passengers are permitted to travel with small amounts of marijuana.

Flying with pot from Vancouver to Montreal, on the other hand, is perfectly legal so long as you meet the age requirement and carry no more than 30 grams of cannabis.

“As long as the flight is domestic, people are allowed to bring a certain quantity for their personal use,” said Canadian Federal Transport Minister Marc Garneau in a statement.

Be aware the age limit across borders can differ as well

To use recreational marijuana in Canada you must be at least 18, although some provinces set their minimum age at 19. The production, distribution or sale of cannabis products is an offense for minors.

However, the minimum age for recreational possession of marijuana in US states where it is legal is 21, adding to the murkiness — and danger — of traveling internationally with a substance prohibited by US federal law.