The measure makes it legal to possess only a prescribed medical grade extract known as CBD or cannabidiol, which is non-intoxicating.
The U.S. Congress in 1972 deemed the oil to have no accepted medical use and banned it.
However, some studies have shown it to be useful in treating a number of conditions, including seizures, and it has been legalized for use in 20 states, according to the Medical Marijuana ProCon website.
Called Carly's Law, the bill in Alabama originated to help control violent seizures suffered by a toddler with a severe neurological disorder.