Which organization is responsible for overseeing substance use treatment regulations in California?

The option identifying the Department of Health Care Services (DHCS) is correct because this agency is charged with overseeing public health in California, which includes the regulation and administration of substance use treatment services. The DHCS is responsible for managing the state's Medi-Cal program and ensuring compliance with federal and state regulations pertaining to substance use disorder treatment and prevention.

This includes licensing facilities, monitoring treatment quality, and overseeing the implementation of treatment programs to ensure they align with the state's health standards and policies. The DHCS collaborates with various stakeholders to develop comprehensive strategies for addressing substance use issues in California, reinforcing its pivotal role in regulating treatment services for addiction.

The other organizations mentioned, while they may play roles related to health or social services, do not hold the specific responsibility for regulating substance use treatment. Thus, they do not have the same level of authority or involvement in the oversight of substance use treatment regulations as the Department of Health Care Services does.