The functions of the Department of Public Safety comprise all administrative functions of the state now or hereafter authorized by law to be exercised, except as otherwise expressly provided by this Chapter, in relation to:

(1) The maintenance of peace and order as involved in the services of police patrol and crime prevention and detection;

(2) Highway traffic control and highway safety;

(3) Police and fire training and investigating as conducted by the state but not the municipalities; and

(4) The enforcement of regulatory provisions of law.  

Nothing in this Part affects in any manner the rights, powers, and duties of the sheriffs or constables of the various parishes or of the marshals or police of all incorporated municipalities.