This argument depends upon how one defines the ‘territorial integrity’ of a state in Article 2. Certainly it would not be legitimate for a state to simply declare based on an old treaty or historic claim that its territory encompassed that of a neighbour and to invade, therefore the requirement to respect territorial integrity must only refer to de facto integrity. Given that Serbia has no actual control over the territory of Kosovo it is not a violation of the rights of the Serbian state to recognise it as an independent nation.