Like HowStuffWorks on Facebook!

How Medical Marijuana Works

Medical Marijuana Laws in the U.S.
A DEA officer holding a marijuana plant
A DEA officer holding a marijuana plant
Doug Menuez/Photodisc/Getty Images

America's first pro-medical marijuana laws were passed in the 1970s. Since then, many such laws have been passed, modified or repealed. Currently, 12 states have medical marijuana laws: Alaska, California, Colorado, Hawaii, Maine, Montana, Nevada, New Mexico, Oregon, Rhode Island, Vermont and Washington [source: Drug Policy Alliance Network]. Maryland has a law authorizing medical marijuana use, but it doesn't allow patients to grow their own marijuana, and patients can still be fined under the law.

Despite these regulations, federal law supersedes state law, so someone can still be arrested and prosecuted for using or possessing medical marijuana, even if it's legal under state law. State laws generally don't legalize buying and selling of marijuana (at least not for profit), but they do legalize possession of it for medical use, following a doctor's recommendation. Medical marijuana laws usually protect from prosecution people designated as caregivers, such as those who take care of sick friends or family members and supply them with medical marijuana. (Again, most laws have a restriction against caregivers' reaping a profit from distributing medical marijuana.) Some of these laws also specify a list of conditions for which marijuana can be recommended.

Another 12 states have laws authorizing some form of medical marijuana research. Thirty states have laws that recognize marijuana's "medical value" [source: Marijuana Policy Project]. Some states have passed laws that have been made ineffective through repeal, overriding federal standards or "watered down" legislation. For example, some state laws authorize doctors to prescribe marijuana for medical use, but since it remains illegal under federal law to prescribe the drug -- and pharmacies can't supply it -- the laws are effectively void.

Let's use Washington as a brief example of one of the 12 states with "effective" medical marijuana laws. The state's Medical Marijuana Act allows a patient, with doctor's recommendation, to grow marijuana for his or her own use -- but only an amount that can be considered, at most, a 60-day supply [source: Washington Citizens of Medical Rights]. The doctor's recommendation is considered valid so long as the doctor continues to act as the patient's health care provider and doesn't revoke the recommendation.

On the next page, we'll take a look at California, the figurative poster child of medical marijuana in the U.S., and at what the FDA has to say about the drug.