Easier than that.
National testing, anyone who gets a trace bigger than X (got to allow for passive actions) gets shot. No 2nd chance, all the assets can be seized to pay for the program and the bullets. We can then extend the program to other substances and target the bankers. Which to be fair are less likely to mug you on the corner of the street for your phone.
Happy to have a pass for the people who use CBD for medical reasons, but if they can found out dealing they still get shot. (entrapment is fine for this as a test as well)
Pretty much win win all the way around. Good training for the royal Navy as well as then can use the floating bodies as target practice (just the lead in the ocean to worry about)
Tell me you live on a council estate without telling me you live on a council estate.