My understanding is that the NSL is a subpoena, and therefore a request for production of documents. It does come with a gag clause however.
Government can only compel you to hand over information for third party which you possess. They can't compel you to DO something, as demonstrated by FBI v Apple recently.
> They can't compel you to DO something, as demonstrated by FBI v Apple recently.
In case anyone who's not familiar with the Apple case is reading this: The government didn't actually wait for the court to rule that they can't (which might or might not be the case, though my understand is that they would've probably ruled in favour of Apple), but rather withdrew the case after a third party unlocked the phone for them.
Just the same, they can compel someone to give over information that enables the FBI to do something on their behalf- private encryption keys or signing certificates, for example.
Government can only compel you to hand over information for third party which you possess. They can't compel you to DO something, as demonstrated by FBI v Apple recently.