California Code, Penal Code - PEN § 264.1

(a) The provisions of Section 264 notwithstanding, when the defendant, voluntarily acting in concert with another person, by force or violence and against the will of the victim, committed an act described in Section 261or 289, either personally or by aiding and abetting the other person, that fact shall be charged in the indictment or information and if found to be true by the jury, upon a jury trial, or if found to be true by the court, upon a court trial, or if admitted by the defendant, the defendant shall suffer confinement in the state prison for five, seven, or nine years.