(a) Except where the Board determines that the public interest requires otherwise, meetings, or portions thereof, shall not be open to public observation where the deliberations concern the issuance of a subponea, the Board's participation in a civil action or proceeding or an arbitration, or the initiation, conduct or disposition by the Board of any matter involving a determination on the record after opportunity for a hearing, or any court proceeding collateral or ancillary thereto.

(b) Except where the Board determines that the public interest requires otherwise, the Board also may close meetings, or portions thereof, when the deliberations concern matters or information falling within the scope of 5 U.S.C. 552b (c)(1) (secret matters concerning national defense or foreign policy); (c)(2) (internal personnel rules and practices); (c)(3) (matters specifically exempted from disclosure by statute); (c)(4) (trade secrets and commercial or financial information obtained from a person and privileged or confidential); (c)(5) (matters of alleged criminal conduct or formal censure); (c)(6) (personal information where disclosure would cause a clearly unwarranted invasion of personal privacy); (c)(7) (certain materials or information from investigatory files compiled for law enforcement purposes); or (c)(9)(B) (disclosure would significantly frustrate implementation of a proposed agency action).