[nitrogen]

At that point you will be willing to give up some of your civil liberties.

This is unlikely. Let's assume for the sake of argument that you have satisfied requirement #1 (proof of a threat). #2 (proof of trustworthiness) and #3 (proof of efficacy and best approach) remain unsatisfied. How is reading my email and leaving vulnerabilities in my software going to prevent a non-state group from buying a WMD?

If we ever reach that point it will be a sign that we have totally failed to build a global enlightened society. I remain unconvinced that universal snooping will even help with that at all, let alone be the most effective approach.