AAV ventilate facing outside on external wall

Is it within code (UPC or Residential) to service and vent an air admitance valve (AAV) to the outside of house? I live in the area of Redmond, WA.

The plumbing is on an external wall and first floor. It seems just as easy to vent externally behind a removable grill as it is inside. I think STUDOR vents are spec'd to be vented internally or externally if not exposed to weather elements.

 

Except for access, I can't think of a good reason to put it outside. The things (when working properly) only let air IN, not out, so there should be no issue with them smelling. IF you smell sewer gasses from it, it is time to replace it. It cannot be the only vent on the system, as there must be some way for air to go out as well.