I think you are looking for section 512(h) of the DMCA.
Thanks for the link. Here is a portion of the key section, as relates to issuance of subpoenas:
(h) Subpoena To Identify Infringer.—
(1) Request.— A copyright owner or a person authorized to act on the owner’s behalf may request the clerk of any United States district court to issue a subpoena to a service provider for identification of an alleged infringer in accordance with this subsection.
(2) Contents of request.— The request may be made by filing with the clerk—