Chevron Products Company (Chevron) (defendant) submitted an application to the City of Richmond (Richmond) (defendant) in California for permits to construct the Chevron Energy and Hydrogen Renewal Project (the Project). The Project’s purpose was to upgrade manufacturing facilities at a Chevron refinery to process a wider variety of crude oil from a wider variety of sources. Richmond began compiling an environmental-impact report (EIR), as required by the California Environmental Quality Act (CEQA), Cal. Pub. Resources Code § 21000. However, in the initial draft of the EIR, Richmond declined to make any finding regarding whether the Project’s greenhouse-gas emissions would have a significant impact on the environment. After objections, Richmond acknowledged the significance of greenhouse-gas emissions but, in the final EIR, still refused to state that the Project’s greenhouse-gas emissions would have a significant impact on the environment. Richmond finally issued a new publication of the EIR, which stated that the Project’s greenhouse-gas emissions would likely have a significant impact on the environment. Because of this admission, the EIR was required under CEQA to describe, evaluate, and adopt mitigating measures. The EIR accordingly put forth a mitigation plan that required Chevron to submit a mitigation plan to Richmond within one year of permit approval. The EIR’s mitigation plan did not require any specific measures from Chevron but rather suggested certain measures from Chevron. Communities for a Better Environment (CBE) (plaintiff) filed a petition for a writ of mandate against Richmond and Chevron, arguing that the EIR was flawed because the EIR had failed to disclose, analyze, and mitigate all potential environmental impacts of the Project. The trial court granted the writ, and the defendants appealed.