(5)
The rights of an exclusive representative under the provisions of this subsection shall not be construed to preclude an employee from—
(A)
being represented by an attorney or other representative, other than the exclusive representative, of the employee’s own choosing in any grievance or appeal action; or
(B)
exercising grievance or appellate rights established by law, rule, or regulation;
except in the case of grievance or appeal procedures negotiated under this chapter.