Rob, the building code that requires safety glazing in your situation should state what panes need to be tempered. It's not a requirement in the IRC. The IRC requires the interior pane to be safety glazing in certain situations, but a WUI is not one of them. I would assume that the perceived danger is from wildfire, so the outer pane would be the one you want tempered, but the code should specify, or your building official should be able to tell you.