There is a shit ton of caselaw surrounding this issue, specifically regarding the vehicle not being in motion and people being in the vehicle with the keys in their possession, etc. It is not "easily fought in court" when it's been determined that there is reverse onus on the accused to prove they were not in care or control.
The section of the criminal code regarding impaired driving states the vehicle does not have to be in motion, that the person merely needs to have care and control of it - and in doing so, they could inadvertently set the vehicle into motion while they are impaired, whether they intended to drive or not.
Numerous people have been convicted of impaired when they are sleeping in the front seat with the keys in their possession, or sitting with the car on, or the keys in the ignition.
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