La. Civ. Code art. 1848
Current with operative changes from the 2024 Third Special Legislative Session
Testimonial or other evidence may not be admitted to negate or vary the contents of an authentic act or an act under private signature. Nevertheless, in the interest of justice, that evidence may be admitted to prove such circumstances as a vice of consent or to prove that the written act was modified by a subsequent and valid oral agreement.
La. C.C. § 1848