"And if a country like Pakistan has a serious extremist problem, then action like that is justified."
When you make a statement like that, it becomes very obvious that you have little idea how extreme the problems are in Pakistan.
Let me make it as clear as I possibly can. The supposed "government" of Pakistan controls less than half of the country. Government troops aren't safe anywhere within the country. They can only move openly in little more than half the country - that is, within the portions they actually control, along with some border regions, and areas where the village chieftains view the government with favor. Elsewhere, within the borders of "Pakistan", the troops only move stealthily, or by air, or in force.
Pakistan is more lawless than Mexico, by an order of magnitude.
The northern areas are controlled by tribal chiefs and by the Taliban.
Now, you tell ME how serious the situation in Pakistan is.
Next, you can tell me what the chances are that the government is going to EFFECTIVELY enforce their edicts regarding these cellphones.
You do remember that Osama bin Laden was killed, living a life of relative luxury, inside the borders of Pakistan?