In re Andre R. (1984) 158 Cal. App. 3d 336 analyzed Penal Code section 12021.5 which provided, in pertinent part, " 'a minor may not possess a concealable firearm unless he or she has the written permission of his or her parent or guardian to have such firearm or is accompanied by his or her parent or guardian while he or she has such firearm in his or her possession.' " (158 Cal. App. 3d at pp. 340-341.) The court determined that the People did not bear the burden of proving that the defendant did not have the permission of a parent to possess the firearm at issue. The court explained, "it is well established that where a statute first defines an offense in unconditional terms and then specifies an exception to its operation, the exception is an affirmative defense to be raised and proved by the defendant." ( Id. at p. 341.) The pertinent inquiry is whether the matter excepted is so incorporated as to become a part of the enacting clause. Unless so incorporated, it is a matter of defense. "Here, the existence of written parental permission does not define or describe the offense." ( Id. at p. 342.) Moreover, the existence of written permission is a fact peculiarly within defendant's knowledge. Thus, subjecting him to the burden of producing exonerating evidence would not be unduly harsh or unfair. (Ibid.)