You are in an adversary and need documents from a third person (not a party to the lawsuit). You issue upon him a subpoena with the discovery request for documents (subpoena duces tecum). He ignores it. What do you need to do? If your knee-jerk reaction was “…I’d file a motion to compel!” then you’d be wrong. The answer is ….
If the 3rd party ignores the subpoena — it is a contempt proceeding, so you have to file a motion for an order to show cause re: contempt per LBR 9020-1. (cue dramatic music).