Canadian cannabis entrepreneurs and investors could face a lifetime ban from the US over their involvement in the industry, US media report.
A senior US border official told news site Politico that Canadians in the burgeoning sector could be deemed inadmissible to the US.
Canada is a month away from becoming the first industrialised nation to legalise recreational cannabis use.
While some US states allow pot use, the drug remains federally illegal.
There have been concerns within Canada's growing cannabis industry for months that they may face trouble crossing the border.
In July, a Vancouver businessman was banned from entering the US for life because he had investments in US marijuana companies.