A rare example of exception that is. As long as GC do not posess wicked intentions on Bretonian authority, I don't see a problem for them to co-operate against a common opponent. Think about the Xenos fighting the OC off of New York with the navy and resuming their usual skirmish after repelling them, which is a short-term and slightly similar example of the case. However, the defaultness of ID definitions may play a contradictory role.