[lke]

It seems to me that as far as international rules go it's not an "abuse" of power. National airspace is, after all, national. You can refuse entery to a foreign president if you damn well please. (High ranking official have a very limited liberty of movment since every deplacment abroad is subject to authorisation of the receiving country.)

On the other hand once you have authorising them to cross your airspace usually grants them extra-territoriality. Meaning that for an reglementary standpoint you can't force a plane to land and search it. (No suspending authorisation once the plane is in the airspace, and you can't search the plane because it is considered foreign territory.

(note this is what i understand of this matter, and may not be exact)