I think either is OK though I myself rather choose 'a rule never to break'.
English to-infinitive clauses are really messy when they are used as a post-modifier [adjective] of a noun. I have been always annoyed (in writing) with a problem; 'NOUN to Do': NOUN is Do's subject or Do's object? My rule is that NOUN is Do's object when the sentence of "O
The usage of English to-infinitives is really messy. I'm sure you know it very well but let me confirm our knowledge.
NOUN+to infinitive. The moderator to ask is Pieanne.=The moderator who we should ask is Pieanne. Pianne got a message to reply = Pieanne got a message that she should reply. My wife has a meal to prepare.[not to be pr