California Code, Evidence Code - EVID § 523

In any action where the state is a party, regardless of who is the moving party, where (a) the boundary of land patented or otherwise granted by the state is in dispute, or (b) the validity of any state patent or grant dated prior to 1950 is in dispute, the state shall have the burden of proof on all issues relating to the historic locations of rivers, streams, and other water bodies and the authority of the state in issuing the patent or grant.

This section is not intended to nor shall it be construed to supersede existing statutes governing disputes where the state is a party and regarding title to real property.