On the event "a unit leaves region", you can order it to go back in.
Or teleport it back inside.
Or kill it instantly.
Or summon two Abominations that will kick its sorry hide until it runs back inside by itself...
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.