The amendment to the Commerce, Justice and Science appropriations bill seeks to overturn a 2011 directive from the Bureau of Alcohol, Tobacco, Firearms and Explosives that stated "any person who uses or is addicted to marijuana, regardless of whether his or her state has passed legislation authorizing marijuana use for medicinal purposes, is an unlawful user of or addicted to a controlled substance, and is prohibited by federal law from possessing firearms or ammunition."

The proposed amendment by Sen John Walsh, D-Mont., would prohibit the use of federal funds to prosecute gun owners based on their status as registered medical marijuana patients in states that allow medical use of the drug. The measure does not cover recreational marijuana users in Colorado and Washington, two states that have legalized limited recreational use by adults.