La. Stat. tit. 32 § 395
Except as otherwise provided by law or by this Chapter, authorized agents of the commissioner shall not be impeded from exercising the functions of their office or performing their duties in the enforcement of this Chapter, the regulations of the department or of the commissioner adopted pursuant hereto, or any other law of this state within the scope of their authority upon any highway, whether or not the highway is located in whole or in part within the corporate limits of any incorporated municipality of whatsoever population or within any parish of this state. However, in doing so, they shall observe the traffic and police regulations of such municipalities and parishes and, whatever practicably possible, shall cooperate with the police departments of such municipalities or parish officials who shall aid and assist them in the enforcement of this Chapter.
La. R.S. § 32:395