Cal. Gov. Code § 50606

If the legislative body decides to proceed, it shall by ordinance fix and establish the boundaries of the district, declare that the district is formed pursuant to this chapter, describe the open areas to be maintained by the district, order the maintenance to be performed and provide that the cost and expense of doing the maintenance shall be paid by annual assessments upon the land within the district. The ordinance forming the district shall be final and conclusive on all persons in all particulars.