If a traveler admits to past use of any drugs that are illegal in the USA, such as marijuana, he or she will be found inadmissible.
Also, marijuana residue - which can linger inside of a vehicle - could possibly be detected by inspection dogs and lead to further questioning.
People with connections to Canada's nascent legal cannabis industry say they're increasingly concerned about the prospect of a lifetime travel ban from the United States.
Typically, travellers will be given the opportunity to "voluntary withdraw" from the border, or they face an "expedited removal".
Hurricane Florence prompts Waffle House to activate storm center
At the front of the room, three screens showed storm maps and news coverage of Category 4 hurricane's path. "That's really bad. For their part, Waffle House is glad that they can serve as a barometer of the severity of the storm for the community.
However, Owen, who oversees U.S border operations, said the traveler would still be able to apply for a waiver from the lifetime ban, which can takes months to be processed and costs $585. Companies hiring new employees should ask prospective hires if they have any current or past connection to the marijuana industry that could put them in the crosshairs of US border officials, he said.
In his interview with Politico, Owen added that Canadians should not expect cannabis-related questions as a matter of routine while crossing the border. USA officials also warn that any form of participation in the sector could likewise cause someone to be turned away, signaling potential problems for investors.
"I think it's incredibly unsafe for someone to [lie], especially if they are somebody who works in the industry and their affiliation with the industry is readily available online", said Enenajor.
"Although medical and recreational marijuana may be legal in some U.S. States and Canada, the sale, possession, production and distribution of marijuana remain illegal under U.S. federal law", Niezgoda said.
"Every country has the right to judge who gets to come into their borders or not".
"A lot of people don't understand that they are still going to have problems after legalization", said Henry Chang, a partner at Blaney McMurtry LLP in Toronto who handles immigration law on both sides of the border.