I just got this from Keith Stroup, Legal Counsel for NORML:
Washington, DC: The 2010 edition of the White House National Drug Control Strategy, released this week, calls on states to enact laws criminalizing motorists who drive with the residual presence of drug or inactive drug metabolite in their body.
"Fifteen states (editor's note: actual total is 17) have passed laws clarifying that the presence of any illegal drug in a driver's body is per se evidence of impaired driving," the report states. "ONDCP (White House Office of National Drug Control Policy) will work to expand the use of this standard to other states and explore other ways to increase the enforcement of existing DUID (driving under the influence of drugs) laws."
Experts have criticized the implementation of per se DUID laws for cannabis because the drug's metabolites may remain present in urine for weeks or months after past use. Studies have consistently reported that the presence of marijuana metabolites is not associated with psychomotor impairment or an elevated risk of motor accident.
By contrast, one international study has estimated per se THC blood levels for occasional marijuana users. However, a more recent study reported that chronic cannabis consumers can have residual levels of THC in blood for up to a week after past use. Authors argued that this unusually long half-life limits the implementation of statewide per se standards for marijuana.
To date, the only study to assess the impact of per se drugged driving laws on behavior found that the enforcement of such policies has "done nothing to reduce DUID or deter the typical offender."
Commenting on the 2010 National Drug Control Strategy, NORML Deputy Director Paul Armentano said, "While driving under the influence of illicit and licit substances is arguably an issue worthy of legislative concern, the expansion of zero-tolerant or arbitrary per se laws – particularly for cannabis – neither addresses the problem nor offers a legitimate solution. At best, it is an inappropriate, inflexible response to a negligible social ill. At worst, it is a cynical attempt to misuse the traffic safety laws to further discriminate against and prosecute cannabis consumers for what they choose to put in their bodies."