An IP is not a person. NSA knows the entrance to internet, but they dont know who uses this entrance.
The sweet thing about secret agencies is that they don't need to KNOW who uses that ip, they only need to guess correctly. And even when they don't guess correctly, you still can be catched in their net wrongly.
They are not the police. They don't need to prove that you are guilty. They catch you away and you rot in some hidden prison. If they are not so sure about you then they will ask you, maybe abu ghraib style?
thats right, they dont need to know things concretely to "arrest" or detain you.
And once they do, all they have to do is coerce the info they need about you, or raid your house and take your computers, phones, etc and find whatever they want. Good luck hiding behind an ip address
I m talking about a democratic country, not a dictatorship like USA. Well, in my country if the converment raid the houses of the citizens, this means civil war. Do you know what is civil war?