Richmond, Virginia has broken new ground in the zone game with proposed "Target Enforcement Zones" that would banish "previously arrested" prostitutes and johns from certain areas. The Times-Dispatch makes no mention of mobility rights or due process, but a Richmond police officer helpfully explains, "This allows us to identify an individual to the court and say, 'You can't be in this area.'"
Hookers tend to be uneasy about the idea of legalizing the sex trade in part because they fear zoning laws, which would likely restrict them to remote and dangerous neighborhoods. But given that zoning laws are now routinely used to jack up penalties for illegal activities, as with drug-free zones, and to restrict particular people from particular areas, as with sex offender residency requirements, keeping an activity underground is no longer a surefire way to avoid zealous line-drawers.
As I wrote in June, it's not hard to see how this sort of thing will turn out: A zone may push an activity out of one neighborhood and into another for a short time, at which point the latter locality will insist on the same restrictive zone laws to deal with its new influx of victimless crime, and so on. But when zones blanket a massive chunk of urban land–as with New Haven's drug-free zones–you're just back where you started, albeit with harsher penalties for all.