Canadians who travel to the U.S. for reasons related to the marijuana industry “may be deemed inadmissible” at the border, according to U.S. Customs and Border Protection.

Canada’s legalization of recreational cannabis, which takes effect Oct. 17, has raised questions about whether people working in the industry could face problems at the U.S. border, where pot remains illegal at the federal level.

Canadian citizens who work in the legal marijuana industry and come to the U.S. for reasons unrelated to work “will generally be admissible to the U.S.,” the agency said in a statement dated Oct. 9. “However, if a traveler is found to be coming to the U.S. for reasons related to the marijuana industry, they may be deemed inadmissible.”

Canadians spent US$19.8 billion on tourism south of the border in 2016, according to the International Trade Administration. A growing number of Canadians are employed by the cannabis industry, which now includes over 135 publicly traded companies.

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