|He looks totally serious to me|
In the recent elections, the American air attacks on Pakistan were a major issue. All the candidates wanted the people to believe they would do something about the drones. The PPP had no credibility in this area - they had tacitly agreed to American air attacks against Pakistani villages in the north for years. On the other side, Imram Khan's PTI was the full-throated voice of the Pakistani people in raging opposition to the attacks. The eventual victor, Nawaz Sharif, has expressed firm opposition to the drone attacks, but it is far from certain how, or if, that will manifest itself now that he is Prime Minister.
It's a fairly straightforward question. The US is not at war with Pakistan, and bombing another nation is generally considered an act of war. Repeatedly bombing another nation is certainly indicative of a state of war. Pakistan has a well equipped, modern air force and air defense system as a result of its longstanding fear of war with India. The drones in use cannot operate in contested airspace. They are not stealthy, they carry no air-to-air defensive capability and they operate at very low speeds and altitude. They are vulnerable to ground fire and fighters, but it would probably be most effective to go after them with attack helicopters.
The fact that Pakistan does not defend its airspace from these incursions by officially unidentified aircraft is all the proof one needs that they are complicit in the attacks. That makes the endless condemnations of their government and military a farce, and leaves the whole situation messy and unstable. It will be very interesting to see what PM Sharif does at this point. If there is an agreement with the US, he was certainly not a party to it and would not be bound by it. He could officially terminate it and tell the US Military Liaison that they will, henceforth, shoot down unknown aircraft in their airspace. The US could not retaliate directly for the 'offense' of air defense - every nation has that right. It's also interesting that President Obama's speech announcing significant changes to US drone policy came as Sharif was elected - they may have a deal with him already, but for a much more limited program. Still, there have been two attacks since his election - that doesn't seem terribly 'limited' - so it continues to be an open question if Pakistan will end the bombing.
No matter what happens this month, the status quo doesn't seem sustainable. Pakistan's government cannot go on pretending to oppose an American air war they refuse to defend their own nation against, particularly in the face of increasing public anger. It's a fair assumption that there is a quid pro quo involved, and that the US would find ways to make Pakistan suffer if they put an end to the killing, but it can sometimes be surprising where political courage can be found. I'll be the first to admit that an authoritarian steel magnate with a sketchy political history would be a very surprising nationalist hero, but time will tell.