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 Colorado, marijuana is legal for both recreational and medical use. Colorado was one of the first states to legalize recreational marijuana with the passage of Amendment 64 in 2012. Adults aged 21 and over are allowed to possess up to one ounce of marijuana, and they can also grow up to six marijuana plants, with no more than three mature plants at a time. The state has established a regulated market for marijuana, where licensed dispensaries can sell cannabis products. Medical marijuana has been legal in Colorado since 2000, following the passage of Amendment 20, which allows patients with certain qualifying conditions to use marijuana for medicinal purposes. Despite state laws legalizing and regulating marijuana, it remains a controlled substance under federal law, as per 21 U.S.C. §812, and federal law prohibits its possession, use, and distribution. However, the federal government has generally taken a hands-off approach to enforcing federal marijuana laws in states that have legalized it under their own laws.