A. If a person dies after June 22, 2001, leaving an instrument in the form of a testament that was executed prior to June 22, 2001, then a disinherison in that instrument that would be valid under the provisions of Civil Code Articles 1617 through 1626 shall be governed by the provisions of those Articles.
B. If the disinherison would not be valid under the provisions of Civil Code Articles 1617 through 1626, the disinherison shall be governed by the law in effect at the time of the execution of the instrument.