State Preemption of Local Zoning in California
How California state law overrides local zoning ordinances. ADU preemption, lot split preemption, and impact on city-level regulations.
Statewide ADU Preemption Applies
State law establishes statewide preemption standards that supersede local regulations. The citation and source below confirm the verified legal basis.
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.
California 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.
Compare all 51 jurisdictions: ADU preemption table · Short-term rental preemption table
ADU Preemption
This law preempts local ordinances — cities cannot impose rules stricter than the state ADU standard. Effective 2020-01-01.
What local governments cannot restrict:
- ADUs permitted by-right on all single-family and multifamily residential lots — no discretionary review allowed · Source
- Ministerial approval within 60 days required · Source
- ADUs cannot be sold separately from primary dwelling (except under SB 9 lot split) · Source
- Cities cannot require owner-occupied primary residence as condition of ADU approval · Source
Lot Split Preemption
Senate Bill 9 (SB 9) — California Urban Lot Split (effective 2022-01-01)
How Preemption Affects California Cities
State preemption applies to every incorporated city and unincorporated area in California. Select a city below to see how state preemption interacts with local zoning rules.
Source: California ADU Law (Government Code Chapter 13, §§66310–66342). Last verified April 3, 2026. View source