California Code, Elections Code - ELEC § 9282

(a) For measures placed on the ballot by petition, the persons filing an initiative petition pursuant to this article may file a written argument in favor of the ordinance, and the legislative body may submit an argument against the ordinance.

(b) For measures placed on the ballot by the legislative body, the legislative body, or a member or members of the legislative body authorized by that body, or an individual voter who is eligible to vote on the measure, or bona fide association of citizens, or a combination of voters and associations, may file a written argument for or against any city measure.

(c) An argument shall not exceed 300 words in length.

(d) The city elections official shall include the following statement on the front cover, or if none, on the heading of the first page, of the printed arguments:

“Arguments in support or opposition of the proposed laws are the opinions of the authors.”

(e) The city elections official shall enclose a printed copy of both arguments with each voter information guide, but only those arguments filed pursuant to this section shall be printed and enclosed with the voter information guide. The printed arguments are “official matter” within the meaning of Section 13303.

(f) Printed arguments submitted to voters in accordance with this section shall be titled either “Argument In Favor Of Measure ____” or “Argument Against Measure ____,” accordingly, the blank spaces being filled in only with the letter or number, if any, designating the measure. At the discretion of the elections official, the word “Proposition” may be substituted for the word “Measure” in these titles.