Four years ago, Pennsylvania allowed patients suffering from any of 17 serious medical conditions to relieve their symptoms with marijuana. But there was a catch: If they used cannabis as a medicine, they could no longer legally drive.
Last week, the Pennsylvania House of Representatives approved a bill that would eliminate that legal disability by requiring evidence of impairment to convict medical marijuana patients of driving under the influence. That reform points the way to an overdue reevaluation of DUI laws that irrationally and unfairly punish cannabis consumers who pose no threat to public safety.
Thirty-three states have legalized medical marijuana, and 11 have taken the further step of allowing recreational use. The list is likely to grow next week when voters in five states will consider marijuana initiatives.
Even as pot prohibition continues to crumble across the country, many states are still treating sober cannabis consumers as if they were intoxicated. Under Pennsylvania’s current rule, any driver with a tiny amount of THC or an inactive metabolite in his blood (one nanogram per milliliter) is automatically guilty of DUI.
Eleven states are even stricter than Pennsylvania, making it illegal to drive with any amount of THC or its metabolites in your blood. Because those chemicals can be detected long after marijuana’s psychoactive effects have worn off, that “zero tolerance” policy is akin to prohibiting all drinkers from driving, even when they are sober.
Half a dozen states, including Pennsylvania, have “per se” laws that define DUI based on the concentration of THC in a driver’s blood, while one (Colorado) allows an inference of guilt when that level reaches five nanograms per milliliter. But these laws don’t make sense either.
Because THC, unlike alcohol, is fat-soluble rather than water-soluble, there is no clear or consistent relationship between THC in the