Esther 1:19
"If then it seem good to the king, let him make a royal decree, and let it be written according to the laws of the Medes and Persians, and let him not alter [it]: and let not the queen come in to him any more; and let the king give her royalty to a woman better than she."
Is Esther wrong about Persian law being irrevocable?
It is noted that there is no evidence outside of the OT (here, and in Daniel) that Persian law was irrevocable. As scholars note, however, such absolute power "is presupposed by any imperial dictatorship." There is certainly nothing unlikely about such a principle being in force.