Should Per Se Limits Be Imposed For Cannabis? Equating Cannabinoid Blood Concentrations with Actual Driver Impairment: Practical Limitations and Concerns

Fourteen US states have amended their longstanding, effect-based DUI drug laws to per se or zero tolerant per se statutes in regard to cannabis. Other states are considering enacting similar legislation. Under these amended traffic safety laws, it is a criminal violation for one to operate a motor vehicle with trace levels of cannabinoids or their metabolites in his or her blood or urine. Opponents of per se cannabinoid limits argue that neither the presence of cannabinoids nor their metabolites are appropriate or consistent predictors of behavioral or psychomotor impairment. They further argue that the imposition of such per se limits may result in the criminal conviction of individuals who may have previously consumed cannabis at some unspecified point in time, but were no longer under its influence. As more states enact statutory changes allowing for the legal use of cannabis under certain circumstances, there is a growing need to re-examine the appropriateness of these proposed per se standards for cannabinoids and their metabolites because the imposition of such limits may, in some instances, inadvertently criminalize behavior that poses no threat to traffic safety, such as the state-sanctioned private consumption of cannabis by adults