Maybe this has been updated recently but looks like 1500 pounds is the requirement in California for brakes.
Trailer Brakes
In California, brakes are required on any trailer coach or camp trailer having a gross weight of 1500 lbs. or more. Usually the braking capacity on tow vehicles is good; however, it may not be good enough to safely stop the several hundred to several thousand additional pounds that your trailer weighs. Most conventional and fifth-wheel trailers have electric brakes, activated by a controller in the tow vehicle. The controller automatically coordinates the tow vehicle and trailer braking so the two systems work together when the brake pedal is applied.
https://www.dmv.ca.gov/portal/handbo...railer-safely/
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