La. R.S. 39:1177

The certificates of indebtedness may be sold at either private or public sale within the discretion of the issuing bodies but no certificate shall be sold for less than par plus accrued interest to the date of delivery, and no certificate shall bear a greater rate of interest than six per cent per annum, payable semi-annually, or annually within the discretion of the issuing body, or run for a longer period than twenty-five years from its date.