California Code, Government Code - GOV § 66451.10

(a) Notwithstanding Section 66424, except as is otherwise provided for in this article, two or more contiguous parcels or units of land which have been created under the provisions of this division, or any prior law regulating the division of land, or a local ordinance enacted pursuant thereto, or which were not subject to those provisions at the time of their creation, shall not be deemed merged by virtue of the fact that the contiguous parcels or units are held by the same owner, and no further proceeding under the provisions of this division or a local ordinance enacted pursuant thereto shall be required for the purpose of sale, lease, or financing of the contiguous parcels or units, or any of them.

(b) This article shall provide the sole and exclusive authority for local agency initiated merger of contiguous parcels.  On and after January 1, 1984, parcels may be merged by local agencies only in accordance with the authority and procedures prescribed by this article.  This exclusive authority does not, however, abrogate or limit the authority of a local agency or a subdivider with respect to the following procedures within this division: