Greenwarden of Murasa and changing controller
Hey all! I was talking to a local player about this situation, and this ruling came up. I'm reasonably certain I know the answer to this question and I told the player the answer, but when he asked me to justify my answer with CR I was unable to, so I'm wondering if my initial answer was correct, and if so (or if not), how to justify it with CR:
Player A controls Player B's Greenwarden of Murasa. Greenwarden dies. I know Player A controls the trigger even if Player B is the owner of the card, but does Player A have the option to exercise the ability by exiling Greenwarden from Player B's graveyard?
I believe the answer is no, but I can't justify my answer with CR which makes me believe I may be mistaken. Am I?
Thanks!