Yeah, sure...but they already do that. :-) Despite the law. Besides, I would still be in favour of charging a person for the infraction of driving under the influence (of either dope or liquor)...because then he is a threat to other people...and the potential crime is no longer victimless.
So where do we disagree?
What I am saying is that the law should not have the right to invade people's homes and arrest them...for drinking a drink, growing a marijuana plant, smoking a cigarette, reading pornography, possessing an ounce for private use, or smoking a joint. The law has no business coming into someone's home like that, because that someone has not committed a crime against anyone and is not about to. If they're driving on a public road that's a whole different matter. They are then in a position to directly affect other people.