Wrong. The role of the police is to enforce the law.
If the law says you are not allowed to be in possession of certain substances that you are in possession of, then you have committed a crime and the police can arrest you for it. End of story.
> Passing a law against drug use is pre-crime when the only real justification for the law is to prevent other crimes.
It is not pre-crime. By definition, pre-crime is arresting someone before breaking the law. If possession/use is illegal and you do either of those things, you have committed a crime.
I repeat: You have already committed a crime if you use/possess illegal drugs. It cannot be pre-crime in such a scenario.
Also, it's perfectly reasonable and practical to make something illegal because it leads to other (more damaging) actions.
This is not the role of the police. Their role is solely punishment and deterrence.
And if drug use leads to other crimes and other crimes leads to punishment then they're already providing that deterrent, to the thing we actually want to deter.
If you want to prevent drug abuse in response to economic woes etc. then try building more housing and otherwise lowering the cost of living.
> BTW, if it's a crime to use certain drugs, and you use those drugs and are arrested, and that arrest prevents further crimes, this was NOT an example of "pre-crime". You committed a crime. You used illegal drugs.
Passing a law against drug use is pre-crime when the only real justification for the law is to prevent other crimes.