Whose idea was that law? If I were the king and someone discovered resurrection, I’d say that if I die, I get resurrected and keep my kinghood. Likewise if I conquer an area and become a king after it already exists.

Does it at least not apply to cloning? That’s the only way to avoid old age as far as I know, and I can’t imagine kings would be in favor of a law that requires they grow old and die.