YOU ARE REQUESTED NOT TO DISCLOSE THE EXISTENCE OF THIS SUBPOENA INDEFINITELY AS ANY SUCH DISCLOSURE COULD INTERFERE WITH AN ONGOING INVESTIGATION AND ENFORCEMENT OF THE LAW.

And here we are reading it in full. You can’t blame them for trying, but it’s still funny watching them stomp around trying to intimidate people when they have no legal authority.

Notice that they use the term request which in itself acknowledges that they can't actually require it.