A person may be charged with disorderly conduct if s/he invades the privacy of another by peeping through a door or window.
Text of the Statute
Cal. Penal Code § 647(i):
“Every person who commits any of the following acts is guilty of disorderly conduct, a misdemeanor: […]
(i) Who, while loitering, prowling, or wandering upon the private property of another, at any time, peeks in the door or window of any inhabited building or structure, without visible or lawful business with the owner or occupant.
Research is ongoing.