Legislative Background: reforms to the Transportation Provisions of the Criminal Code (Bill C-46)

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Annex 3 – International approaches to THC and driving

United States

Colorado
If a driver has a THC level of 5 ng/ml or more then the trier of fact may infer that they were impaired, but is not required to do so. Colorado is currently engaged in a pilot project involving oral fluid screening devices, but they are not currently authorized for use in a law enforcement context.
Washington
Washington prohibits driving with a 5 ng/ml of THC in the blood. Washington does not authorize the use of oral fluid screening devices.
Montana
A driver who has a THC level of 5 ng/ml or more is presumed to be impaired.
Nevada
The threshold limits are 2 ng/ml in blood and 10 ng/ml of marijuana metabolite in urine but prosecution must prove the driver was under the influence of the drug.
Ohio
The limits are 2 ng/ml in blood and 10 ng/ml of marijuana metabolite in urine.
Pennsylvania
The limit is 1 ng/ml of blood.
California
The limit is 5 ng/ml of blood but there must be corroborating evidence of impairment.

United Kingdom

The UK set a per se limit of 2 ng/ml of blood. The UK has a very limited medical defence for users of prescription drugs which contain cannabis-based elements. The UK authorizes the use of oral fluid drug screening devices for THC and cocaine; a positive result on an oral fluid screener results in a demand for a blood sample.

Ireland

Ireland recently enacted new offences for drugs and driving including driving with 1 ng/ml THC. A person who has a “medical exemption certificate” is not subject to the offence. Ireland authorizes roadside drug screening for cannabis, cocaine, opiates (e.g. heroin, morphine) and benzodiazepines (e.g. valium).

Australia

Australia authorizes random roadside oral fluid screening. A positive result on an oral fluid screener (with a second saliva sample confirming drug presence by the lab) is sufficient to prove the offence of driving with the presence of a prohibited drug in the body.

New Zealand

New Zealand prohibits the presence of THC in a blood sample in situations where a driver has also failed roadside sobriety tests. New Zealand does not authorize the use of roadside drug screeners.