Yesterday the Michigan Supreme Court ruled that state law prohibits operation of a motor vehicle by anyone with a detectable amount of the THC metabolite 11-carboxy-THC in his body. Although 11-carboxy-THC is not psychoactive and can remain in the blood and urine, depending on frequency of use, for days or weeks after any driving-relevant impairment has worn off, the court concluded that it counted as a marijuana "derivative," for which the legal rule is zero tolerance. The upshot is that many regular pot smokers in Michigan can never legally drive, whether they're intoxicated or not. Even occasional smokers will routinely break the law unless they refrain from driving for several days after smoking.
The dissenters were troubled by these implications, but the majority was not:
It is irrelevant that an 'ordinary' marijuana smoker allegedly does not know that 11-carboxy-THC could last in his or her body for weeks. It is also irrelevant that a person might not be able to drive long after any possible impairment from ingesting marijuana has worn off. The use of marijuana is classified as a misdemeanor under current law...The Legislature's prohibition of the operation of a motor vehicle with any amount of marijuana, which explicitly includes derivatives of marijuana, in the body provides more than adequate notice regarding the prohibited conduct.
This is the sort of "per se" policy the federal government wants every state to adopt, by the way.
[via Drug Law Blog]