well a subpoena is generated from something, they just don't hand them out. so again, the reason for the subpoena will be known. duh!!!!
They actually
do just hand them out.
This is how it works.
A lawyer in a case (civil or criminal) will decide that there is some relevant and important information that they would like to have. They will go to the Clerk of the Court's office, and be given a blank subpoena form. The lawyer will fill the form out, going into detail about what documents they are requesting, or what people they are requesting affidavits from. They will then hand those documents to a process server, who will serve it to the person in question.
That person, at that point, is obligated under law to respond to that subpoena - by either producing the documents, or filing a motion to quash the subpoena. To successfully quash the subpoena, they would have to prove that either (1) The documents requested are irrelevant to the issue in front of the court, or (2) the documents are
privileged - in this context, referring to communication between a party to the case and his attorney.
In this case, it would be nearly impossible for Nunberg's lawyers to argue for either of those.