Go ahead and downvote me, but NSA has a different process than warrants for a reason. There is signoff which satisfies the constitution. Secret court, secret panel. It is secret for a reason and the court is overseen by congress.
However personally I would prefer these cases to be declassified after a reasonalbe amount of time, where it is possible to protect the innocent.
Then perhaps you're under the misunderstanding that a judge has signed off on the NSL's. That is not the case, these are warrantless searches.
https://en.wikipedia.org/wiki/National_security_letter
https://en.wikipedia.org/wiki/Fourth_Amendment_to_the_United...