The offense of unlawfully transferring a firearm (Pen. Code, § 12072, subd. (d)) does not require proof that the defendant knew of or should have known that the other party to the transaction was unlicensed. Vaughn, a convicted felon, sold Martin a rifle. Neither Vaughn nor Martin were licensed firearms dealers, but Vaughn testified that he assumed Martin was a licensed dealer because Martin told him he sold guns on the Internet. Vaughn was convicted of being a felon in possession (former Pen. Code, § 12021, subd. (a)(1)) and unlawfully transferring a firearm (former Pen. Code, § 12072, subd. (d)). He appealed, arguing that the jury had not been instructed that it had to find he transferred the rifle to Martin knowing Martin was unlicensed. Held: Affirmed. Section 12072, subdivision (d), does not contain a mens rea component. Generally, a penal statute that does not contain a mens rea element will be construed to include one, but there are exceptions for certain public welfare offenses that are purely regulatory. When the Legislative intent regarding mens rea is not clear, courts will consider the factors in In re Jennings (2004) 34 Cal.4th 254. Here, the first factor, the legislative history and context, weighed heavily against reading a mens rea component into section 12072, subdivision (d), because other subdivisions in section 12072, which regulate different aspects of firearms transactions, include mens rea components. Thus, “when the Legislature intended the violation of a certain provision of section 12072 to require [a mens rea component], it expressly included the requirement.” The court concluded that the remaining Jennings factors (severity of the punishment, the seriousness of harm to the public, the defendant’s opportunity to ascertain the relevant facts, the difficulty prosecutors would have in proving a mental state for the crime), did not outweigh this conclusion. Although a reasonable mistake of fact defense was available under Jennings, there was no substantial evidence that Vaughn’s mistake was reasonable.