My question involves criminal law for the state of: LA

would like advice concerning the following law:

"§63.3. Entry on or remaining in places or on land after being forbidden

A. No person shall without authority go into or upon or remain in or upon or attempt to go into or upon or remain in or upon any structure, watercraft, or any other movable, or immovable property, which belongs to another, including public buildings and structures, ferries, and bridges, or any part, portion, or area thereof, after having been forbidden to do so, either orally or in writing, including by means of any sign hereinafter described, by any owner, lessee, or custodian of the property or by any other authorized person. For the purposes of this Section, the above mentioned sign means a sign or signs posted on or in the structure, watercraft, or any other movable, or immovable property, including public buildings and structures, ferries and bridges, or part, portion or area thereof, at a place or places where such sign or signs may be reasonably expected to be seen.

what stipulations need to be followed concerning this law and public property? Do you need to do anything or can you just be told to leave and have to comply? it does not make sense as written because you would need no justifiable reason to ban someone from public property. any actual cases of this available for review?