In less than three months, Californians will vote on legalizing production, distribution and possession of recreational cannabis. Tax revenues are central to that debate, but the really important question is not so much what taxes would be best today but how those taxes should evolve over time.

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What many people don’t realize is that even if voters reject Proposition 64, state and local officials will still need to deal with cannabis taxes because California’s medical cannabis market is undergoing enormous reforms. The new regulatory regime is expected to start licensing for-profit firms to supply medical cannabis in 2018.

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One innovative option, suggested years ago by Rob MacCoun, a Stanford Law School professor, is to tax cannabis based on its power to intoxicate, such as levying a tax of $12 per gram of delta-9-tetrahydrocannabinol (THC, the cannabinoid most responsible for getting users high). To the extent being intoxicated increases the probability of harm, using taxes to control THC consumption could be a critical policy lever.