Mendocino County, CA Outdoor Lighting: Light Trespass (2026)

Mendocino County does not have a stand-alone, county-wide 'light trespass' ordinance setting numeric limits on light crossing property lines. The most directly applicable rule is in the Coastal Zone: Coastal Zoning Code Section 20.504.035 (Exterior Lighting Regulations) requires exterior lighting to be shielded and directed downward, which by design reduces glare and light spill onto adjacent properties and into the night sky. Within designated highly scenic areas (Section 20.504.015), coastal development permits commonly include conditions confirming that all exterior lighting is downcast and shielded. Together, these coastal provisions function as the County's main tool against light trespass on the coast and are enforced through the Coastal Development Permit and code-enforcement processes. Outside the Coastal Zone, there is no comprehensive inland lighting standard governing spillover between private properties; discretionary projects may be conditioned to control glare during their review, and chronic glare onto a neighbor's property may be addressed as a private nuisance under California law rather than under a specific county lighting code. Practical steps for any property owner include using fully shielded, downward-aimed fixtures, lower-output lamps, motion sensors and timers, and aiming security lights away from neighboring homes. Coastal property owners should confirm the lighting conditions of their Coastal Development Permit, and anyone unsure of their zone should check with Planning & Building Services.