As you may already know, cannabis is a Schedule I controlled substance. This means any possession and use is prohibited by federal law. Unfortunately, Maryland state law cannot prevent state-legal marijuana users from being federally prosecuted for violating the federal Controlled Substances Act. If they choose to do so, The U.S. Department of Justice (DOJ) has the authority and ability to prosecute Maryland MMJ patients. Even so, this doesn't mean that such prosecution is likely. In fact, legislation for the federal government budget, first passed in 2014, explicitly forbids the DOJ from spending federal budget money to prosecute entities that comply with their state's medical marijuana program.