The notice requirements of § 2.28 of this subpart will not apply if:

(a) The information has been lawfully published or officially made available to the public;

(b) Disclosure of the information is required or prohibited by a statute other than the FOIA or by a regulation (other than this part) issued in accordance with the requirements of Executive Order 12600; or

(c) The bureau has exercised due diligence to notify the submitter, but its efforts were unsuccessful.