Cannabis-related stocks dropped in after-hours trading Thursday following a report that the U.S. may bar Canadians who invest in the companies from entering the U.S. Politico reported Thursday afternoon that an official with the U.S. Customs and Border Protection agency said that Canadians who smoke marijuana, work in the industry or invest in the companies could be permanently banned from the U.S. "Facilitating the proliferation of the legal marijuana industry in U.S. states where it is deemed legal or Canada may affect an individual's admissibility to the U.S.," Todd Owen, executive assistant commissioner for the Office of Field Operations at the CBP, told Politico. Marijuana use will officially become legal in Canada on Oct. 17. The CBP did not immediately respond to an email seeking to confirm the statements. Stocks that immediately declined in late trading included Tilray Inc. TLRY, -12.39% , which declined more than 5%; Canopy Growth Corp. CGC, -8.97% , which dropped about 4%; and Cronos Group Inc. CRON, -4.89% , which also fell about 4%.