LINCOLN, Neb. (AP) — Several Nebraska lawmakers say the state Legislature should approve a bill that would let them regulate medical marijuana before voters legalize the substance.

Senators began debate on the measure Wednesday but are unlikely to vote unless supporters prove they have at least 33 votes to end a filibuster. Opponents of the measure say scientists, not lawmakers, should approve drugs.

A petition now circulating in the state would amend Nebraska’s constitution to give residents the use, buy and sell marijuana and prohibit any laws restricting it. The proposal could come before voters in 2018.

Twenty-nine states already allow marijuana for medical purposes.