Warning letters from the federal government about medical marijuana laws have prompted several states to start reevaluating their laws, USA Today reports. The recent letters from U.S. attorneys indicate that people involved in the growing, dispensing and regulating of medical marijuana have the potential to be prosecuted—even if they are following state laws.

One such warning letter prompted Washington state Governor Chris Gregoire to veto a proposal to create licensed marijuana dispensaries, the article says.

The letter to Gregoire warned that state employees would not be exempt from prosecution if they regulated medical marijuana. Although no state workers have been charged under federal law for regulating medical marijuana, Gregoire said she didn’t want to risk it, according to the newspaper. Gregoire, who is Chair of the National Governors Association, says she wants to work with other governors to change federal law so that medical marijuana is reclassified at a Schedule 2 substance, along with morphine and oxycodone.

Warning letters have also been sent to officials in California, Colorado, Montana and Rhode Island. In Montana, federal authorities recently conducted raids at growing facilities, and last week targeted dispensaries in Spokane, WA, the article states.

The medical use of marijuana, which is not legal under federal law, has been approved in more than a dozen states, USA Today notes.

The article says the Justice Department issued a statement that prosecutors will not allow significant drug-trafficking organizations to shield their illegal operations by pretending they are medical dispensaries