They go and look at the European models, where every prisoner coming into prison is supplied with a needle and syringe, which is put on the wall of the cell. Drug use is still illegal, but if it occurs, it's going to occur without that needle and syringe being shared with 15 other people. It also removes the hazards to the guards, who at the moment are at risk of getting stuck when they do cell searches. It is possible to do it; it does happen in many jurisdictions, and it works.
The other thing that is always raised in objection is that these needles and syringes will be used as weapons, and that has not occurred in the European system.