There was some ruling when the lower court ruled that if police offices saw two guys fighting with knives in a picture window, they still had to ask for a search warrant to enter. The higher court said that was ridiculous and overturned it.
That's because the higher courts are (a) idiots or (b) involved in the degradation of the Constitution.
The NSA's crap would never fly if they had the slightest respect for the fourth amendment, so I'm inclined to say the latter. (Besides, the police have no obligation to protect any private citizen, why should such protection apply, circumventing the 4th, because they wish it?)