The way that I try to handle grey area when I am GM is that I do a quick rules check to see if it's already been clarified one way or the other, and if no solution is found fairly quickly, I go by the basics of "what makes the most logical sense" and "will x solution allow the flow of the game to proceed without unreasonable disruption." Ultimately players will always find a way to break a situation, and it's up to the GM to be able to think on their feet sometimes to ensure that the flow and fun of the table can proceed.
