Iron rules can be described using a variety of different synonyms, each of which carries its own distinct connotations. Some possible alternatives to "iron rules" might include "rigid guidelines," "inflexible parameters," "unshakable standards," or "non-negotiable mandates." Each of these phrases emphasizes the idea of a strict and unbending set of rules that must be followed without exception. Other possible synonyms might include "hard and fast rules," "fixed principles," "unyielding requirements," or "firm directives." These phrases all suggest a sense of unwavering determination and a commitment to maintaining a consistent and predictable standard of behavior.