5 C.F.R. § 5901.102
(b) Definition of “employment.”
(1) For the purposes of this section, “employment” means any form of non-Federal employment or business relationship involving the provision of personal services by the employee for direct, indirect, or deferred compensation other than reimbursement of actual and necessary expenses. It also includes, irrespective of compensation, the following outside activities:
(2) The definition does not include participation in the activities of a nonprofit charitable, religious, professional, social, fraternal, educational, recreational, public service or civic organization, unless:
(c) Procedure for requesting approval.
(1) Requests for approval of outside employment shall be sent to either the DAEO or the Alternate DAEO through the employee's normal supervisory channels and shall include the following information:
(d) Prohibited outside employment.
(1) Employees shall not engage in:
(i) Rendering legal advice regarding, or preparing an individual or group in any matter relating to, labor relations in either the private or public sector, outside the employee's official duties. This prohibition shall not apply to a special Government employee unless he or she:
(2) Exceptions. Nothing in this paragraph (d) prevents an employee from: