Notwithstanding the provisions of subdivision (c) of Section 23306, a county may be created from the territory of Nevada County provided that the territory which is proposed to be transferred from such county does not exceed 25 percent of the total territory of such county.
Source:
Section 23306.5, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV§ionNum=23306.5..