The rules for stances on p. 154 say " To choose an action that stipulates a specific ring, the character must be in the matching stance."
The Martial Arts skills sections say that a character can use Martial Arts to strike using any approach... buuuuuut they also specify some kinds of attacks associated with different approaches. For example, the Overwhelm approach for Ranged can be used for "Firing to create openings," and the Withstand approach for Melee says "fighting defensively".
Does this mean you can't fight defensively in Fire Stance, or create openings in the Earth stance? Seems like that'd be really difficult to regulate/interpret, especially since actions like Guard, Charge, and Strike aren't restricted to particular stances. That said, this sort of restriction might keep people from using only their best ring for every action. Thoughts?