Marijuana—also known as marihuana or cannabis—is classified as a controlled substance under federal law, and its possession, use, and distribution is illegal. See 21 U.S.C. §812.

But many states have recently passed laws that generally legalize marijuana in some form. For example, Alaska, California, Colorado, Illinois, Maine, Massachusetts, Michigan, Nevada, Oregon, Vermont, and Washington have enacted laws legalizing marijuana for recreational use.

The District of Columbia allows all citizens over the age of 21 to possess up to two ounces of marijuana, to use and grow marijuana on private property, and to exchange marijuana between persons as long as no money, goods, or services are exchanged.

And some states that do not allow recreational use of marijuana do allow limited use of marijuana to treat symptoms of illness and other conditions—known as medical marijuana. States that allow limited use of medical marijuana include Arkansas, Arizona, Connecticut, Delaware, Florida, Hawaii, Louisiana, Maryland, Massachusetts, Minnesota, Missouri, Montana, New Hampshire, New Jersey, New Mexico, New York, North Dakota, Ohio, Oklahoma, Pennsylvania, Rhode Island, Utah, Vermont, and West Virginia. The medical marijuana laws in some of these states are broader than others, with some states only allowing use of cannabis-infused products such as oils and pills. Federal law prohibits health care practitioners from writing a prescription for medical marijuana, so practitioners in medical marijuana states write a recommendation for medical marijuana.

Other states have not legalized marijuana, but have decriminalized it—meaning possession of small amounts of marijuana is not punishable by jail or prison time, but may be punished with a fine. States that have decriminalized possession of marijuana under limited circumstances include Connecticut, Maryland, Mississippi, Nebraska, New Hampshire, New Mexico, New York, North Carolina, and Virginia.

Marijuana laws are generally located in a state’s statutes—often in the penal or criminal code, or in the health and safety code.

In Hawaii, marijuana is classified as a Schedule I controlled substance under federal law, which makes its possession, use, and distribution illegal according to 21 U.S.C. §812. However, Hawaii has diverged from federal law by legalizing the use of medical marijuana. The state allows individuals with qualifying medical conditions to use marijuana for medicinal purposes. Patients must obtain a recommendation from a licensed physician and register with the state's medical marijuana program to legally possess and use medical cannabis. Hawaii has not legalized marijuana for recreational use, but it has decriminalized the possession of small amounts of marijuana. As of January 11, 2020, possession of three grams or less of marijuana is no longer a criminal offense and is punishable by a fine of $130, rather than jail time. It's important to note that despite state laws permitting medical use and decriminalizing possession, federal law still prohibits the use, possession, and distribution of marijuana, and federal law enforcement agencies may enforce these prohibitions in Hawaii.