The Australians do have zero tolerance. It is an illegal drug in Australia. They don't want you mixing it with your driving, so it is definitely zero tolerance. We find it in your oral fluid. Now you must recall that oral fluid is going to reflect recent use, because taking a brownie takes a lot longer to be digested and work it's way in. If you find it in oral fluid, you almost undoubtedly have a person who has recently smoked marijuana. And you smoke marijuana, as I understand it, in order to get high, which may not be a good idea if you're planning to drive. The Department of Justice calls it a “precautionary approach”, based on public safety considerations. We prefer to avoid zero tolerance.
On September 27th, 2017. See this statement in context.