Subpoenas may also be served by registered or certified mail or statutory overnight delivery, and the return receipt shall constitute prima facie proof of service. Service upon a party may be made by serving the party's counsel of record. Once issued, a subpoena may be quashed by a Tribunal Judge if it appears that the subpoena is unreasonable or oppressive, or that the testimony, documents, or objects sought are irrelevant, immaterial, or cumulative and unnecessary to a party's preparation and presentation of its position at the proceeding, or that basic fairness dictates that the subpoena should not be enforced. The Tribunal Judge may require the party issuing the subpoena to advance the reasonable cost of producing the documents or objects.
Ga. Comp. R. & Regs. R. 616-1-3-.22
O.C.G.A. §§ 50-13A-13(d),(f).