They have the technology to create a location based memory wiping system that is thwarted by a specific person, chosen at random, walking across it?
Specific people can convey memories by touch based on a tattoo/birthmark on ones wrist?
They have the technology to build said city with 100% climate control, but can't geo-tag people in it with remote kill (sorry, 'moved on to elsewhere') capability to prevent said memory bubble bursting?
Technology to create UAV's with real time control and atractor beam