I think for the most part, rules describe what you can do. Then where necessary, restrictions are made within this framework; for example, the Rule of 4, which limits how many cards you can draw in the fellowship phase.
So going by this:
- You can perform game text if the rules don't prohibit it. Example: Playing companions outside the fellowship phase. The rules don't prohibit you from playing them outside the fellowship phase--they just don't give you a built-in way of doing so.
- You can perform game text if it acknowledges somehow the rule that's being broken, or can only work with it broken. Example: Using
Sent Back to play Gandalf when a copy is in the dead pile ("even if another copy of that wizard is in your dead pile").
That's the gist of it I think, though there are issues like
O Elbereth! Gilthoniel! not working without the need for errata. But for this topic, IMO the wording of
Pass of Caradhras is not enough to break the rule Lurtzy quoted. Play a weather card... provided there isn't a rule prohibiting said card from being played that phase.