CA Prob Code Section 101

(a)

Upon the death of a married person domiciled in this state, one-half of the decedent’s quasi-community property belongs to the surviving spouse and the other half belongs to the decedent.

(b)

Notwithstanding subdivision (a), a husband and wife may agree in writing to divide their quasi-community property on the basis of a non pro rata division of the aggregate value of the quasi-community property, or on the basis of a division of each individual item or asset of quasi-community property, or partly on each basis. Nothing in this subdivision shall be construed to require this written agreement in order to permit or recognize a non pro rata division of quasi-community property.