According to reports, there were 4 helicopters used in the raid on Osama Bin Laden. They apparently left from Ghazni.
Is it conceivable that even one helicopter could be flown so close to the capital of another country without raising alarm bells?
Considering these were military helicopters and there were four of them, I am skeptical that this would be allowed. Surely the airspace in Pakistan is monitored just as well as other countries?