My Tenant asked to changed the locks at the house he is renting. I told him "no". I went out to the property today for some maintence and did give the tenant 36 hours notice, and when I tried to go into the house, I found out the locks had been changed. How do I go about getting a key for this house for maintence purposes? And is this legal in the State of Lousisana.. . City of Slidell?

Well I would have hired a lock shop to open the doors, and I would have put new locks on the building and charged the tenant with all of the bills,

And perhaps given the tenant a eviction notice for doing it against your permission.

The last thing I would have done would have been walked away without going in that day.

No its not legal for the tenant to change the locks without permission. Deliver a notice to the tenants that, if you do not receive a copy of the key within 24 hours, you will show up the next day with a locksmith to change the locks again and they will be responsible for the costs involved.