Cal. Gov. Code § 66905.5
As used in this title:
"Region" includes that part of Lake Tahoe within the jurisdiction of the State of California, the adjacent parts of the Counties of El Dorado and Placer lying within the Tahoe Basin in the State of California, and that additional and adjacent part of the County of Placer outside of the Tahoe Basin in the State of California which lies southward and eastward of a line starting at the intersection of the basin crestline and the north boundary of Section 1, thence west to the northwest corner of Section 3, thence south to the intersection of the basin crestline and the west boundary of Section 10; all sections referring to Township 15 North, Range 16 East, MDB&M. The region defined and described herein shall be as precisely delineated on official maps of the agency.
Ca. Gov. Code § 66905.5