I went back and looked at the actual statute. In fact, it very well may be. The relevant section is below...
CAL. PEN. CODE § 261.5If they're having sex, he's guilty of misdemeanor statutory rape. It's only a misdemeanor because he falls within the three year age limit.(a)Unlawful sexual intercourse is an act of sexual intercourse accomplished with a person who is not the spouse of the perpetrator, if the person is a minor. For the purposes of this section, a "minor" is a person under the age of 18 years and an "adult" is a person who is at least 18 years of age.
(b)Any person who engages in an act of unlawful sexual intercourse with a minor who is not more than three years older or three years younger than the perpetrator, is guilty of a misdemeanor.