In the United States, marijuana is illegal on a federal level for any purpose, be it adult use or medicinal. Cannabis is listed as a "Schedule I" controlled substance, meaning it is classified as having a high potential for abuse and no accepted medical use.
However, despite marijuana’s illegal status federally, the majority of states in the US have legalized cannabis for medicinal or adult use. In 2013, the Justice Department said it would not sue to block laws legalizing cannabis at the state level as long as states enact regulations that curtail underage sales, interstate trafficking, illegal cartel and gang activity, and excessive cannabis-related accidents and violence.
This tenuous "trust but verify" policy has largely remained in place, with the federal government generally declining to devote resources toward enforcing federal laws in legal states.