This is where libertarianism and legalisation would have worked.

Drugs are bad, addictive, will kill you, will turn you into a criminal......

Well so say the do gooders and control freaks that make decisions in this country, the ones who wish to control our lives and make sure that we do as we're told. One of those aspects is the making of certain drugs illegal, thus criminalising a subset of people and driving them into the arms of dealers who overcharge and don't do quality checks.

Guardian.

A lethal batch of heroin contaminated by anthrax has emerged in London and Germany, and has now claimed 10 lives, two months after cases emerged in Glasgow.

The Health Protection agency said that an unnamed heroin user is being treated in a London hospital after becoming ill last month, in the first known case of anthrax being caught through drug use in England.

Investigators also confirmed that the anthrax which killed a drug user in Germany in December was indistinguishable from the strain confirmed to be in 14 of the 19 cases so far in Scotland, where nine addicts have died.

The odd thing is, statistics prove the vast majority of casual drug takers aren't addicts, at least not in the way of becoming thieves, being unable to do their jobs and taking to the streets to live in cardboard boxes. In pretty much the same way that most people who like a drink aren't alcoholics.
This is why most (though not all) libertarians favour the legalisation of drugs. They can then be taxed, quality controlled and the users registered at a chemist/doctors and their health monitored. It's essentially a win/win situation as the criminal classes who prey on vulnerable users will be put out of business or will be forced into other areas, the same would work for the sex industry (if industry is the right term. Legalise it, monitor it, control it, then tax it.
Yes I know some people out there will think we are corrupting society or minors, but over all I think it will lead to a better society and certainly fewer opportunities for a criminal underclass to prosper and abuse their clients/slaves.
That's not to say that some will not abuse the legalisation, but then again there are some who drink themselves to death even now.
So, what's stopping the government? It's not like they haven't tried to probe and control every aspect of our lives now is it?
I suspect they fear some sort of moral outrage, perhaps sanctions from abroad, I'm not sure, but certainly what appears to be a good idea is blocked by political intransigence and lack of will.