Charles Ellicott Commentary Esther 1:19

"If it please the king, let there go forth a royal commandment from him, and let it be written among the laws of the Persians and the Medes, that it be not altered, that Vashti come no more before king Ahasuerus; and let the king give her royal estate unto another that is better than she." — Esther 1:19 (ASV)

That it be not altered. —Literally, that it not pass away. The order having been committed to writing was, in theory at any rate, immutable. The best illustration is the well-known case of Daniel; see also below (Esther 8:8). Probably a strong-willed monarch would interpret this inviolability rather freely.