I really do not like the whole nanny state philosophy.
The government job is to supply accurate information not to protect people from themselves.
If a person using drugs commits a crime against another person or someone elses property then they should be restrained or prosecuted for that act but it is not the governments role to decide for the indiviudal on the basis of this might lead to some undesirable consequence.
Children who are unable to make reasonalb decisions of risk versus benefit are a special case as always.
At heart I am a libertarian, with government of limited scope and powers and a maximum of personal freedom. With such freedom comes acceptance of the consequences and responsiblity for the choices you make. If you want to take drugs it is not the governments business unless you commit some other crime against another person or someone elses property.