California Code, Harbors and Navigation Code - HNC § 782

(a) Excepting laws regulating the discharge of sewage into or upon the navigable waters of any lake, reservoir, or freshwater impoundment of this state, and notwithstanding Section 660, no vessel, as defined in subdivision (e) of Section 775.5, is subject to any other state or local government law, ordinance, or regulation with respect to the design, manufacture, installation, or use within any vessel of any marine sanitation device.

(b) Notwithstanding any other provision of law, nothing in this chapter precludes or restricts a city, county, or other public agency from adopting rules and regulations with respect to the discharge of sewage from vessels.

(c) State and local peace officers may enforce state laws relating to marine sanitation devices and may inspect vessels if there is reasonable cause to suspect noncompliance with those laws.

(d) A state or local peace officer who reasonably suspects that a vessel is discharging sewage in an area where the discharge is prohibited may board that vessel, if the owner or operator is aboard, for the purpose of inspecting the marine sanitation device for proper operation and placing a dye tablet in the holding tank.