In November 2016, California voters legalized recreational marijuana use by passing the “Adult Use of Marijuana Act” (also known as “Proposition 64”). In the wake of legalization, many people are concerned about marijuana users on California roadways. But how, if at all, does marijuana decriminalization affect California DUI law?
The short answer is that it has no effect. Here's why.
In California, it’s illegal to drive a vehicle while under the influence of marijuana, or any other drug. Under California law, a person is “under the influence” if the substance ingested by the person “so far affected the nervous system, the brain, or muscles as to impair to an appreciable degree the ability to operate a vehicle in a manner like that of an ordinarily prudent and cautious person in full possession of his faculties.” (Cal. Veh. Code § 23152(e) (2016); Byrd v. Mun. Court, 125 Cal. App.3d 1054 (1981).)
So, anyone who drives while impaired by marijuana can be convicted of a DUI. That the driver may have ingested marijuana legally doesn’t matter. To dispel any doubt, the new legislation explicitly says that the decriminalization of marijuana doesn’t affect California DUI or BUI (boating under the influence) law. (See Cal. Health & Safety Code § 11362.45 (2016).)