Several U.S. states have started reassessing their medical marijuana laws after stern warnings from the federal government that everyone from licensed growers to regulators could be subjected to prosecution. The Department of Justice said two years ago that it would be an inefficient use of funds to target people who are in clear compliance with state law. But U.S. attorneys have said in their recent memos that they would consider civil or criminal penalties for those who run large-scale operations — even if they are acceptable under state law.