Also I just looked up the penal code for California. Yup, according to the law chalk fits the definition
594. (a) Every person who maliciously commits any of the following
acts with respect to any real or personal property not his or her
own, in cases other than those specified by state law, is guilty of
vandalism:
(1) Defaces with graffiti or other inscribed material.
(2) Damages.
(3) Destroys.
As used in this section, the term "graffiti or other inscribed
material" includes any unauthorized inscription, word, figure, mark,
or design, that is written, marked, etched, scratched, drawn, or
painted on real or personal property.