Arizona Republic:  “Because of restrictive zoning rules, most medical-marijuana sites will be situated in industrial areas, far from prying eyes, foot traffic and passing cars. Cities made every effort to create distance between the marijuana operations and homes, schools, churches, parks and other similar facilities.  As a result, even though medical-marijuana locations are allowed in zoning categories that cover most shopping areas, the distancing rules pose a serious hurdle.”

This story has an interesting table that summarizes the zoning applications in several large Arizona cities.