La. Code Civ. P. Ann. art. § 1091

SECTION 4.  INTERVENTION

Art. 1091.  Third person may intervene

A third person having an interest therein may intervene in a pending action to enforce a right related to or connected with the object of the pending action against one or more of the parties thereto by:

(1)  Joining with plaintiff in demanding the same or similar relief against the defendant;

(2)  Uniting with defendant in resisting the plaintiff's demand; or

(3)  Opposing both plaintiff and defendant.