Can a felon in possession of a concealable weapon stop a prosecution for such crime by attacking the validity of the underlying felony?

For example, a felon in possession of a firearm cannot halt a prosecution for such crime by attacking the validity of the underlying felony, because the offense is based on that person's status at the time of possession. (See People v. Harty (1985) 173 Cal.App.3d 493, 499500, 219 Cal.Rptr. 85 [construing former section 12021; the possible invalidity of an underlying prior felony conviction provides no defense to possession of a concealable weapon by a felon]; see also People v. Sanchez (1989) 211 Cal.App.3d 477, 479481, 259 Cal.Rptr. 294 [equivalent holding construing former section 12021.1].)⁵