Irrevocable means cannot be revoked or recalled, unalterable.
Irrevocable is an adjective.
Synonyms: final, fixed, unchangeable, irreversible, conclusive, permanent, unalterable.
Antonyms: temporary, changeable, reversible, revocable, ephemeral.
I don't think the rule is irrevocable; we can always change it if we decide it is not working.
Our college has an irrevocable commitment to excellence.
Next time, consult me first before you make any irrevocable decision.