Louisiana constitution
Article 6
Section 28

The governing authority of a local governmental subdivision may impose an occupational license tax not greater than that imposed by the state. Those who pay a municipal occupational license tax shall be exempt from a parish occupational license tax in the amount of the municipal tax. The governing authority of a local governmental subdivision may impose an occupational license tax greater than that imposed by the state when authorized by law enacted by the favorable vote of two-thirds of the elected members of each house of the legislature.