CA Gov't Code Section 56768

A petition for detachment of territory from a city shall be signed by either of the following:

(a)

Not less than 25 percent of the registered voters residing within the territory proposed to be detached, as shown on the county register of voters.

(b)

Not less than 25 percent of the number of owners of land within the territory proposed to be detached who also own 25 percent of the assessed value of land within the territory, as shown on the last equalized assessment roll.