Interferometry on the microwave background allows the U.S. military to track all people, weapons, and aqueous objects bigger than a thimble throughout an entire city such as Paris.
Advanced technologies allow them to know when these things are brewing, but per game theory they allow them to happen to not reveal that capability.
Encryption and Snowden have nothing to do with it. They are limited hangouts to gaslight and decrease the power of the lower echelons of government (you know, the regular people who might actually have stopped this).