Drug laws vary in the U.S. by state. To find out whether a drug is legal, it’s best to consult the United States Drug Enforcement Administration (DEA) as well as state, local, and federal laws. Some drugs are illegal for anyone to possess, while others are illegal to use if they’re not prescribed to you by a physician. Some examples of illegal drugs in the U.S. include cocaine, heroin, LSD, and fentanyl.