Gov. Mary Fallin on Monday signed a law that would exempt cannabidiol products from Oklahoma's definition of marijuana if they are approved by the Food and Drug Administration. Cannabidiol products, like those seen in this file photo, are related to marijuana but have no psychoactive effects. [Photo by Steve Gooch, The Oklahoman Archives]

Oklahoma Gov. Mary Fallin signed a bill Monday amending Oklahoma's definition of marijuana.

With House Bill 1559, any federally approved cannabidiol drug or substance will not be considered marijuana. No cannabidiol drug has been approved yet by the Food and Drug Administration, however.

Removing it from the definition of marijuana clarifies its difference from the illegal drug.

Cannabidiol, also known as CBD, is being researched and used as a medicine for some ailments, including severe childhood seizures. This is the third year in a row that Fallin has signed a bill that could expand its use.