California Code, Streets and Highways Code - SHC § 19311.1

(a) The board of supervisors shall not levy assessments pursuant to Section 19311 unless it has adopted an ordinance to do so.  The board of supervisors shall place before the voters of the zone, either before the initial ordinance takes effect or within one year thereafter, the question whether the district shall be authorized to levy assessments.

If the majority of those voting disapprove of such authority, no subsequent ordinance levying assessments for any succeeding fiscal year shall be adopted by the board of supervisors without the prior approval of the voters of the zone.

Subsequent election or elections to secure such approval shall not be held more than once a year.

(b) The approval of the voters may be secured at a district or countywide election, or by a ballot mailed to each property owner or registered voter of the zone.

(c) The proposition is approved if a majority of those voting approve the proposition.