Yes, I'm not sure either. Ideally, if I trusted people, I would be in favour of minimal government intervention in almost every area. But I don't. Generally, people are greedy and stupid, and when they're young, completely naive.
So I think aggressive prohibitions on drugs have the potential to "protect us from ourselves" -- especially children. Surely, if certain drugs are made unattainable to children who would otherwise have tried them (either through real law inforcement, or just the stigma of the substance being illegal), then these people will most certainly be thankful later on in their lives. If the government can act as a parent in some regards, and this has a net benefit, then that is probably good.
The question is whether enforcement is really stopping people from taking drugs. And also, the bureaucracy associated with legalisation. Should these drugs be government produced? Or should they be open to private industry? If open to private industry, isn't there a huge risk of misrepresentation, and so on. And if all drugs are legal, why have prescription medications? The reason prescription drugs aren't accessible "over the counter" is because they will likely be misused by ignorant people. And public health, as a whole, has certainly benefited from this stance: there are millions of ignorant people hoping to self-medicate with powerful drugs which would not help them.
So, I'm not decided. It's not a simple question, and it's not just one question either. Legal for which age groups? Which drugs? Who sells the drugs? etc.