These kids died because they wanted to take drugs and most drugs are illegal. No doubt as a consequence of this illegality they bought mephedrone – legally sold as a plant food online – and it killed them. Their reasons for choosing a legal drug over an illegal one are open to debate – perhaps they didn’t want to break the law, perhaps they had no access to illegal drugs. Either way it brings into question the whole legislation.
The bottom line is kids want to experiment with drugs and no amount of legislation will solve this problem. It is a deep sociological problem that will not be solved by banning certain chemicals. Today it is plant food, tomorrow it will be insect repellent or rat poison. We cannot legislate against every chemical that has some euphoric or hallucinogenic effect. Society has a responsibility to protect kids like this by making their experiments safe until a time when the desire has been removed.