I don't think traffic laws are a very good parallel for what we are really discussing. It's somewhat irrelevant, because high-speed cars are still made and sold so I doubt speed limits ban squat. You simply get caught by a patrol officer and ticketed, which probably adds points to your license. That's not the same as criminalizing smokers.That's just it - by banning it, they reduce the effects of it.
See it this way - maybe you can drive a car at 140 km/h without problems. But that doesn't mean others can. So. They have to think of everyone on the road and thus reduce the maximum speed limit on behalf of the society to reduce death tolls.
The need of many before the need of one. That's how a society works.
And smokers are criminalized in this country because of the tax laws, but that's another topic ...
For what you propose we do, Elysia, America has tried. The war on drugs was Nixon's idea, and frankly with hindsight it has done little more than let 1% of the U.S. population join the prison population because of onerous drug law. We're simply putting voters in jail because they smoke pot on weekends, simply placing the burden of funding substance control on the shoulders of the tax payer. It's to the point now that a majority of the police don't care about the average citizen with a few grams on him. I can testify to that. If the police don't care about a law, forget about it.
Prison shouldn't be a revolving door for drug lords either but for America I think it's high time we step back and realise that cannabis (and perhaps some other drugs) has simply been pushed into an underground economy. It could be regulated as well as cigarettes are.