Any Municipal employee under civil service, other than a common laborer, shall be guilty of misconduct in office and subject to dismissal from service if such employee engages in any business or work or contracts for work, for. hire or for reward, while in the employ of the City. This section shall not apply to any employee who may engage in any work which is in the furtherance of the national defense program of the United States, provided that such Federal defense work in no way conflicts with his regular duties as a Municipal employee.
(1969 Code Sec. 31.11)