Does a defendant have a constitutional right to present highly probative evidence in support of his mistake of law defense?

In sum, the trial court effectively denied defendant his constitutional right to present highly probative evidence in support of his mistake of law defense. (People v. Cunningham (2001) 25 Cal.4th 926, 999 [defendant has due process right to present all relevant evidence of significant value probative to his or her defense].) And, as the People expressly concede, the error was not harmless because the trial court precluded defendant from presenting evidence that, if believed by the jury, would have established a

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mistake of law defense and resulted in an acquittal. Consequently, reversal of both convictions is required.²