GMG's sovereignty over anything is dependent on the Kusari government recognizing it. GMG has whatever right in Honshu it has, because the Kusari government gives it to them. If the Kusari government decided to nationalize Amori and the GMG assists on Planet Honshu, there is very little the GMG can do. If the Kusari government declares the GMG a hostile power, Kishiro would be forced to choose between Kusari and the GMG, and I would assume they would side with Kusari, leaving the GMG without any way to get their product to their costumers, quickly putting the GMG out of business. If the GMG thinks it can stand against the Kusari government they have a harsh lesson coming.
Also, lets make this very clear, Dab does not dictate the policy of the Kusari government, whether he made the system or not. The Kusari government will decide on these things, the way the Kusari government would, in rp, and without worrying about the infocards and such in Okinawa.