Only those things which are prohibited by the Church are prohibited by the Church-- or, put another way, the Church teaches that being fully the sort of Catholic the Church teaches us to be is how to be Catholic, or yet another way, the Church teaches what it teaches, which includes that what it teaches is logically consistent, or another way "Truth does not contradict Truth".
Catholicism is also a public religion-- that is to say, it's not gnostic or otherwise dependent on secret truths known only to elites. There is no apocrypha in the ancient sense, no secret gospels too powerful for the minds of "lesser" men. All of the Church's moral teachings are, as a matter of principle, publicly available, even if they may not always be easily understood, and a bishop refusing to teach someone moral principles in order to keep them secret has something of the flavor of simony to it.
That said, laws hardly ever deal with real things, because they would then be practically unenforceable in the sort of neutral, objective, non-discriminatory way most modern societies want law enforcement to work. A law, for example, might prohibit eating a certain food, gathering in a certain place, or not wearing a certain item of clothing. The Church does not categorically require or permit any of that. However, the Church does categorically forbid sin and categorically extoll virtue and all of those describe both virtuous and wicked actions. The Church, by and large, leaves determining when an action is pernicious and when it is morally obligatory to the prudential judgment of the person making the decision whether or not to take that action. The Church provides advice and teaching and guidelines to help with that-- see e.g https://christianity.stackexchange.com/a/78754/17529 -- but ultimately it is up to the individual practitioner in all but the most exceptional cases to determine what God requires of them and then do it, and in those rare cases where it is really obvious that someone is wrong about that, it's the local pastor who has the primary competence to correct and teach his congregation, not any big centralized body in the Vatican or anything. So, while theoretically only that which the Church forbids is, of course, forbidden by it, practically someone would have to be messing up really, really bad for their specific religious objection to actually not hold up on the grounds that "Catholicism doesn't prohibit that", since almost all actions or non-actions could be a sin and the Church has a lot of respect for the importance of experiential knowledge, prayer, and prudential judgement.