They have to draw blood. And if they even legally can(without a warrant) depends on the state. If there's a legal limit of active THC in the blood varies by state. There's a problem with those limits tough, as someone can have more than the limit in their blood despite having not consumed for days and being perfectly sober.How do you get arrested for driving while high? What is the minimum blood thc level to be legally impaired?
Do they make you piss in a cup? Take a hair sample?
You must not either.You must not live in a state that it was voted in. The smell, the crime, the bullies that do not give a shit about life.