For drug crimes, Louisiana does have mandatory minimum sentences. Certain crimes may go without prison sentencing, while others have minimum sentences by law. For example, if you're found in possession of over 10,000 pounds of marijuana and are convicted of a drug charge, you must complete a minimum 25-year sentence. That particular crime is a felony.
Interestingly, possession of marijuana in particular is not enough to result in a mandatory minimum sentence as long as you're in possession of less than 60 pounds of the drug. There are suggested prison sentence lengths, but a judge may not decide to give you any prison time at all. However, if you're caught distributing or growing marijuana, then you're in a different situation.