State Preemption of Local Zoning in California

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.

ADU Preemption

What local governments cannot restrict:

• ✓ADUs permitted by-right on all single-family and multifamily residential lots — no discretionary review allowed
• ✓Ministerial approval within 60 days required
• ✓ADUs cannot be sold separately from primary dwelling (except under SB 9 lot split)
• ✓Cities cannot require owner-occupied primary residence as condition of ADU approval

Lot Split Preemption

Senate Bill 9 (SB 9) — California Urban Lot Split (effective 2022-01-01): SB 9 (effective January 1, 2022) requires cities to ministerially approve: (1) splitting a single-family lot into two parcels where the original lot is at least 2,400 sqft and the resulting parcels are each at least 1,200 sqft; and (2) building 2 units on each resulting parcel. This effectively allows up to 4 units on a single-family lot via SB 9. The split must be in an urbanized area or urban cluster. Owner must intend to occupy one unit for 3 years. Does not apply to historic districts, coastal zones, high fire hazard zones, earthquake fault zones, or floodplains.

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.