Well, why do regions not have the ability to prevent movement from another region to their own?
That would be an interesting power. It would definitely give people more tools to prevent jumps, or to prevent more infiltration from the same source.
It is also easily circumventable but can still be useful to reduce the viability of set "jump points"
Just add a cap to it(e.g. no more than 5 regions) to reduce server load...