This report is a broad overview of the state of practice in California of greenhouse gas mitigation under the California Environmental Quality Act (CEQA) and, more specifically, the use of off-site measures and carbon offsets for mitigation. The findings in this report are based on a literature review, interviews with key informants, and a review of public environmental documents. The purpose of the report is to inform the California Air Resources Board about the state of practice in support of the mission identified in the 2022 Scoping Plan for Achieving Carbon Neutrality. There are four key findings in the report.

•    The state of practice around greenhouse gas mitigation, especially off-site and carbon offset mitigation, is inconsistent, dynamic, and contested. Moreover, recent CEQA court rulings have created significant confusion over what is legally defensible.

•    Local lead agencies (i.e., cities and counties) and air districts have developed very little guidance for use of off-site and carbon offset mitigation; in fact, most have no guidance.

•    Relatively few EIRs (less than 5%) currently require carbon offsets for mitigation.

•    CEQA practitioners are strongly encouraging the state to develop better guidance possibly through legislation, rule-making, and technical support.