California Penal Code 594 defines Vandalism as: Any 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:

1. Defaces with graffiti or other inscribed material,
2. Damages, or
3. Destroys any real or personal property of another.

Vandalism is a “wobbler”. It is a property crime that the state may charge as a misdemeanor or even a felony. The state will not hesitate to prosecute you for the criminal damage caused by your actions.
That means a wide variety of destructive or unsightly behaviors could be considered vandalism, including seemingly minor crimes like shooting at a stop sign or scratching a name into a desk.

In California, it is illegal to enter any land with intent to injury property, property rights or with intention to interfere, obstruct, or injure any lawful business. It is also illegal to occupy any property not owned by the person without the owner's consent and to refuse to leave private property or to gain unauthorized access of property.