I think keeping them controlled but allowing recreational prescriptions gets you at least part way there. You go to see your doctor, tell him you want to try a

I think keeping them controlled but allowing recreational prescriptions gets you at least part way there. You go to see your doctor, tell him you want to try a particular drug and your reasons for doing so - curiosity or having enjoyed it previously both being legitimate reasons. The doctor reviews your history, discusses any concerns/conflicts with existing medication, and having ensured that you're fully informed, issues you a prescription which entitles you to purchase the drug at your nearest pharmacy and doubles as your license to carry that specific controlled substance. That way, safe intervals can be observed (for example, it's generally recommended that you shouldn't take MDMA more than once every couple of months or so), appropriate recovery/preparatory supplements can be recommended, and dependency can be watched out for.