I was reading an article on a developing situation in one of the most volatile regions in the world and the strained ties between US and Pakistan.
It is being speculated that Pakistan might end American access to their air and land space, completely disrupting American ability to supply their troops Afghanistan.
Former US ambassador Richard Olson said:
Since closing Pakistan’s airspace would hinder America’s ability to defend its forces in Afghanistan, Olson, the former ambassador, said the US might regard such action as a “casus belli,” or grounds for war. Other former US officials echoed that assessment.
That seems like a rather confusing assessment. Isn't it a right of a sovereign state to decide who should they cooperate with? Does it really constitute a valid Casus Belli? By that I mean would that make it a lawful war in the eyes of United Nations and international community? Let's ignore the odds of that happening or implications of such a move and focus purely on the legal aspect.
Anglo-Soviet invasion of Iran comes to mind when Allies invaded Iran to secure a route to supply Soviets against the rapidly advancing Germans so historical precedent does exist although from times before UN.
My question is basically, Does refusal to let Country A supply their troops by Country B constitute a legally valid casus belli as per international laws and norms? If my understanding is correct, the only wars considered lawful by the UN are defensive wars or the ones sanctioned by her, assuming of course that UN has the final say in international law.
I emphasize that my interest in it is purely legal, I am not interested at all in the eventuality of this happening, or the background of US-Pakistan issues etc.