Cannabis became legal in Canada on October 17, 2018. Anytime something becomes legal, there is a framework created for its legal use; when you fall outside of this framework, the activity becomes illegal. We’ve covered a lot of the issues pertaining to the legalization of cannabis on the blog already, but we haven’t gone in depth on what might be one of the most important — and contentious — issues. It is illegal to drive high. What exactly that means is made clear by legislation, but it’s unclear whether or not that legislative framework actually works.

Here’s the framework: you cannot drive with 2 or more nanograms (ng) of THC per ml of blood. Between 2 and 5 ng THC/ml of blood, you face a maximum fine of 1000$, unless there is also alcohol in your blood. For individuals with over 5 ng THC/ml blood, or individuals with (50+ mg alcohol/ml of blood) + (2.5+ ng THC/ml blood), you face much steeper penalties, including a mandatory minimum 1000$ fine for a first offense and 30 days imprisonment for a second offense. Here’s a more complete list of alcohol and cannabis related impaired driving charges.

The main problem with this legislative framework is how THC is processed by the system, and how it can be detected. THC is a complex molecule, more so than alcohol, and the method by which you consume it will also change how it affects you. You won’t see a chart explaining how many puffs you can take before you reach the legal limit, because one person might process the THC quite rapidly, while another might have it linger in their bloodstream. Additionally, how impaired a person gets is not necessarily clear based on how much THC is in their bloodstream; some folks might be impaired for hours after the THC has left their bloodstream, while others might not be impaired while it’s still present.

THC will enter and leave the bloodstream in relatively short order; it usually peaks in the bloodstream about 3–10 minutes after inhalation, but about 1–2 hours after being ingested. THC is fat soluble, unlike alcohol, which is water soluble. That means detecting alcohol in the bloodstream is a much more accurate measure of how much can be consumed; THC, on the other hand, can enter the bloodstream days after it was consumed, as it’s slowly released by fatty tissues.

There are roadside saliva tests to check for THC. They have not been proven to be accurate. Their accuracy may be impeded by the cold. That means that in order to have an accurate test, a blood sample must be taken and, as we’ve discussed, even that might not be totally accurate. The rules for the level of THC indicate that it cannot be above the stated amounts within 2 hours of driving; what that two hours will do for each person depends highly on their metabolism, level of fat, and frequency of smoking.

You should never drive high. That said, you may be pulled over, get tested, find you have high levels of THC, get a blood test, and find you had THC in your system above the legal limit — even if you weren’t high. What all this boils down to: if you get charged with impaired driving for THC in your system, get an impaired driving defense lawyer. Immediately.