Synonyms and related words :
absolute, binding, commanding, compelling, compulsory, conclusive, decisive, decretal, decretive, dictated, dictating, directive, entailed, final, hard-and-fast, imperative, imposed, instructive, irrevocable, jussive, mandated, mandating, mandatory, must, obligating, obligatory, peremptory, preceptive, prescript, prescriptive, required, ultimate, without appeal,