re: which is it?
The moves in question *are* the moves of the legislators. By constantly banning stuff, the legislators provoke the Chinese labs into cooking up new-different legal stuff, so all the legal highs are always too new for the medical people to know anything about much more than short-term effects.
And as others have pointed out, a constant clinical trial phase before legislating bans would slow down the cycle, but not stop it, and would cost an unreasonable amount of money.
Legalising some list of drugs beyond those already explicitly legal (ethanol, nicotine, caffeine, theobromine, etc.) would have a number of interesting effects:
* An increase in the safety of each legalised substance, as the tendency is for illegal drugs to be cut with, well, random stuff that you don't know what it is.
* An increase in tax revenue, as you can apply the same sort of taxes to these drugs as you apply to the existing legal drugs.
* A short term spike in the quantity consumed, as people experiment with the new explicitly-legal high, followed by a drop. The final level is difficult to predict, but probably would be similar to now.
* A down-spike in the quantity consumed of the remaining illegal drugs, as people switch from illegal expensive stuff with uncertain contaminants to cheaper legal stuff with regulated content.
* A reduction in certain types of crime, as it becomes less necessary to do that stuff in order to pay for drugs.
The list to be legalised is difficult to assess, as the edges of what's considered OK vary with time, culture, and so on. I don't have any easy solutions there, and it's a difficult set of decisions to make. I'd also say that the current collection of clowns in the UK government aren't up to the job, sadly.