The Globe and Mail reports in its Friday edition that marijuana companies that operate south of the border are facing new worries about legal exposure in the United States after the Department of Justice took steps toward enforcing federal law banning cannabis. The Globe's Christina Pellegrini writes that the move sparked a sell-off of shares in listed pot companies -- even those which do not have any U.S. operations. U.S. Attorney-General Jeff Sessions on Thursday moved to rescind an Obama-era policy that allowed states to let cannabis be grown, sold and used within their borders, handing the decision of when to enforce federal cannabis law to prosecutors in each state. Mr. Sessions's move came mere days after California began allowing the sale of recreational marijuana and amid a stunning surge in pot stocks. An exchange-traded fund that tracks the pot sector rose more than 25 per cent over four days from Dec. 28 to Jan. 3. The move by Mr. Sessions caught the market off guard, but investors should not be surprised. In regulatory filings, companies raised the chance that previous guidelines could be revoked at any time and detailed the legal risks they could face by doing business south of the border.