Washington already had an open container law for alcohol, and now the same theory applies to marijuana. If you have marijuana in your car, it better be in an unopened container from a licensed store, otherwise you get fined. Per King 5:
Washington State troopers are ramping up efforts to enforce a new portion of the state’s marijuana law, which makes it illegal to have an open container of pot in your car.
The law went into affect on Sept. 26 and is similar to the state’s alcohol open container law.
The law states that marijuana must be in its original sealed package and stored in the trunk of your car or behind the backseat. It also extends to pot-infused edibles.
The fine for a violation is $136. This means that not only can you not have an open container from a store in your vehicle, but you basically can’t have any black market marijuana in your vehicle at all because obviously it didn’t come with sealed packaging from a store. Washington residents cannot grow their own, so by default if marijuana is in your car without a store container around, it will be assumed that it came from the black market. The one exception would be medical cannabis that comes from a dispensary. I’m not sure how that works into the equation. I’m curious to see if law enforcement in Washington tries to use this new law to try to find angles. I guess only time will tell.