California Penal Code section 528.5 makes some forms of impersonation a misdemeanor punishable by ip to a year in the county jail. Take a look at the actual code section below (current when I wrote this) to see what’s illegal to do, but remember that even acts not technically violating this law might violate others so be careful!
PC 528.5. (a) Notwithstanding any other provision of law, any person who knowingly and without consent credibly impersonates another actual person through or on an Internet Web site or by other electronic means for purposes of harming, intimidating, threatening, or defrauding another person is guilty of a public offense punishable pursuant to subdivision (d).
(b) For purposes of this section, an impersonation is credible if another person would reasonably believe, or did reasonably believe, that the defendant was or is the person who was impersonated. (c) For purposes of this section, “electronic means” shall include opening an e-mail account or an account or profile on a social networking Internet Web site in another person’s name.
(d) A violation of subdivision (a) is punishable by a fine not exceeding one thousand dollars ($1,000), or by imprisonment in a county jail not exceeding one year, or by both that fine and imprisonment.
(e) In addition to any other civil remedy available, a person who suffers damage or loss by reason of a violation of subdivision (a) may bring a civil action against the violator for compensatory damages and injunctive relief or other equitable relief pursuant to paragraphs (1), (2), (4), and (5) of subdivision (e) and subdivision (g) of Section 502.
(f) This section shall not preclude prosecution under any other law.