California Code, Penal Code - PEN § 1127d

(a) In any criminal prosecution for the crime of rape, or for violation of Section 261.5, or for an attempt to commit, or assault with intent to commit, any such crime, the jury shall not be instructed that it may be inferred that a person who has previously consented to sexual intercourse with persons other than the defendant or with the defendant would be therefore more likely to consent to sexual intercourse again.However, if evidence was received that the victim consented to and did engage in sexual intercourse with the defendant on one or more occasions prior to that charged against the defendant in this case, the jury shall be instructed that this evidence may be considered only as it relates to the question of whether the victim consented to the act of intercourse charged against the defendant in the case, or whether the defendant had a good faith reasonable belief that the victim consented to the act of sexual intercourse. The jury shall be instructed that it shall not consider this evidence for any other purpose.

(b) A jury shall not be instructed that the prior sexual conduct in and of itself of the complaining witness may be considered in determining the credibility of the witness pursuant to Chapter 6 (commencing with Section 780) of Division 6 of the Evidence Code.