An employee shall not participate, while on Government- or TVA-owned or leased property or while on TVA duty, in any gambling activity including the operation of a gambling device, in conducting a lottery or pool, in a game for money or property, or in selling or purchasing a numbers slip or ticket. However, this section does not preclude activities:

(a) Necessitated by an employee's law enforcement duties; or

(b) Under section 7 of Executive Order 12353 (47 FR 12785, 3 CFR, 1982 Comp., p. 139) and similar TVA-approved activities.