1. Half the law enforcement, out of the job.
2. Half the lawyers and the judges, out of the job.
3. Half the privatized prison system, out of the job.
4. A few million other jobs that support and/or depend on the above, done away with.
It's pointless to even try this in the USA... No one is going to be willing to give up the ongoing and ever-giving spoils of the war on drugs.
Let see ... there is the $3/hour farm hand shortage going around in a few states.
Or do you mean all the new jobs that are going to be created, you know, just-like-that? For which they'll be re-trained, just-like-that? For which they'll get the same pay/benefits, just-like-that?
So the real question is how many people are employed by the war-on-drugs, and how many of them can be re-asigned, and how willing will they be to let this happen.
http://en.wikipedia.org/wiki/War_on_drugs#Costs_to_taxpayers
Also, a lot of jobs does not equal half the jobs.