A decree is a rule handed down without discussion. Dream books read it as an inner command — a should or a must — or as a decision made elsewhere that you feel bound to obey.
When this appeared in your dream, what were you feeling?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.