State Preemption of Local Zoning in Arizona
How Arizona state law overrides local zoning ordinances. ADU preemption, lot split preemption, and impact on city-level regulations.
What Is State Preemption?
State preemption occurs when a state law overrides local government ordinances in a specific area. In land use, preemption means a city or county cannot adopt zoning rules that are more restrictive than the state standard. If a city tries to prohibit something the state law permits, the state law wins.
Arizona actively uses preemption in housing law. The state has enacted legislation that prohibits local governments from blocking certain types of housing development — most notably accessory dwelling units (ADUs) and lot splits.
ADU Preemption
Arizona House Bill 2297 (HB 2297)
This law preempts local ordinances — cities cannot impose rules stricter than the state ADU standard. Effective 2024-09-14.
What local governments cannot restrict:
- Partial preemption — cities retain authority over design standards, height limits, and maximum unit size within state-defined bounds
How Preemption Affects Arizona Cities
State preemption applies to every incorporated city and unincorporated area in Arizona. Select a city below to see how state preemption interacts with local zoning rules.
Source: Arizona House Bill 2297 (HB 2297). Last verified April 5, 2026. View source