Government Code § 23202

A boundary line between counties shall not be changed, pursuant to this article, if the change would result in any of the following:

(a) The line to be moved a distance of more than 5 miles from its original location.

(b) A reduction by more than 5 percent in the area of any affected county.

(c) A reduction by more than 5 percent of the population of any affected county, as determined by the State Department of Finance’s most recent estimate of population.