California Code, Public Utilities Code - PUC § 120220.5

The board may provide and maintain by contract with a public agency or by other means, a security force to enforce its regulations, to preserve and protect any public transit system or project financed pursuant to this division, and to preserve and protect the public peace, health, and safety with respect to its system or projects. Alternatively, the board may contract with a private patrol operator licensed pursuant to Chapter 11.5 (commencing with Section 7580) of Division 3 of the Business and Professions Code, with the county sheriff and municipal police departments within the areas described in Section 120054, and with other transit development boards for security, police, and related services.