Reminds me of a quote from Love Actually:
> Hiya kids. Here is an important message from your Uncle Bill. Don't buy drugs. Become a pop star, and they give you them for free.
... except in this case the message is don't do drugs kids, but "grown ups" should (as defined as a state of maturity where you know how the drugs behave, know your limits and can balance your experimentation with fulfilling your societal obligations)
I see this as a bit like speeding. The government sets fairly arbitrary speed limits for different types of road. They do it based on what they think the majority of people can cope with, versus the likelihood of risks, vs the need to get from A to B in a reasonable amount of time. The government hasn't been amazingly scientific about the speed limits, and don't take into account time of day, traffic, weather conditions etc. A healthy, fully-alert person can probably go at 150% of the speed limit on an ambient clear day on an empty road - and do so perfectly safely. But that isn't the message they give people, because it would be impossible to assess person-by-person, minute-by-minute.
And yet, some would consider the above information to be recklessly given, because some people will on read "go at 150% of the speed limit... perfectly safely" and take that as my advice.
So the question is, should it be legal to travel at any speed, provided you feel like you're doing a good job of it? In both cases, misjudgement can be disastrous for yourself and the people around you (and innocent bystanders too)
And when you are talking about something that can alter your perceptions, you would surely need a non-drug-taking associate with you at all times who could give you an honest blow-by-blow assessment of where you are dropping the ball as a "normal" human being, and where your drug-fuelled failings are happening?
When the potential downsides so vastly outweigh the benefits, I can understand why laws take the side they do. That said, I absolutely do think that there are massive downsides to making drugs illegal when taken responsibly. Countries should be realistic about what they can and can't do. If they can't eradicate drug use - and most countries can't - they need to put effort into safeguarding above incarceration.
But I think that's the consensus anyway on most social issues. And it seems to be a lesson that governments globally are very slow to learn.