The issue is that smoking marijuana does impair driving, meaning you shouldn’t drive. The law needs some kind of proof that doesn’t rely on a time machine, so they test your body. Your body can’t really tell you when the thc entered your body, so you get two options:
The test can still prove you were under the influence at some recent-ish moment, so any sufficient amount in your blood means you can’t drive.
The test can’t prove it’s recent enough for you to have been impaired while driving, so it can’t be used as proof, which effectively means you could never be convicted of being under the influence (meaning it’s unenforceable).
The former negatively impacts marijuana users who won’t be able to drive for some time. The latter means people under the influence could drive and due to their impairment hit and kill someone.
Somewhat obviously, the lawmakers have decided that blocking some people from driving is better than letting someone under the influence drive a speedy death machine. So the law doesn’t care whether you were actually impaired; it was in your system, so you’re not allowed to drive.
The issue is that smoking marijuana does impair driving, meaning you shouldn’t drive. The law needs some kind of proof that doesn’t rely on a time machine, so they test your body. Your body can’t really tell you when the thc entered your body, so you get two options:
The former negatively impacts marijuana users who won’t be able to drive for some time. The latter means people under the influence could drive and due to their impairment hit and kill someone.
Somewhat obviously, the lawmakers have decided that blocking some people from driving is better than letting someone under the influence drive a speedy death machine. So the law doesn’t care whether you were actually impaired; it was in your system, so you’re not allowed to drive.