What is a “rare” species? In the context of the California Environmental Quality Act (CEQA) Guidelines, this became a central question in the recent court decision, Nassiri v. City of Lafayette, et al., First District Court of Appeals, June 27, 2024. The Section 15380 definition of “Endangered, Rare or Threatened Species” has long been a part of the Guidelines. This section also mandates lead agencies to consider a species endangered, rare, or threatened if it can be shown to meet the qualifying criteria described therein, even when the species is not listed under either the California Endangered Species Act (CESA) or federal Endangered Species Act (ESA). Public agencies serving as a CEQA lead or responsible agency carry the responsibility to consider a species’ qualification as endangered, rare, or threatened under CEQA based on the facts of the project. This responsibility raises important issues for the environmental practitioner.