Medical Marijuana Patients in Pennsylvania Are at Risk of DUI Charges Pennsylvania law still classifies cannabis as a Schedule 1 controlled substance, even for medical use. That means medical marijuana patients can be charged with DUI simply for having THC or its metabolites in their system, regardless of whether they are impaired. This is because Pennsylvania follows a zero tolerance standard for Schedule 1 and non-prescribed Schedule 2 drugs. No proof of impairment is required. The presence of