People v. Marrero 69 N.Y.2d 382, 507 N.E.2d 1068 (1987) Marrero was a prison guard at a Federal prison in Connecticut. He was arrested for carrying a gun in New York. At Trial Marrero argued that according to New York law, he was allowed to carry a gun. The law specifically exempted "peace officers" including "corrections officers of any State correctional facility or of any penal correctional institution" from the ban on carrying concealed weapons. The problem was that Marrero was a Federal guard, and the Statute only exempted State guards. So he wasn't covered under the exemption. The Trial Court convicted Marrero of carrying an concealed weapon. He appealed. Marrero argued that he honestly believed that the Statute applied to him, and that his subjective belief should exempt him from criminal liability. That's known as a mistake of law. The Appellate Court upheld the conviction. Marrero appealed. The New York Supreme Court upheld the conviction. The New York Supreme Court looked to the historical common-law and the New York Penal Code (Penal Law §15.20) and found that misconstruing a Statute, or making a mistake of law, does not relieve a person of criminal liability. However, the Court noted that if there had been an official statement of the law contained in the Statute or another enactment, and you relied on that interpretation, then you could be exempt from criminal liability. Marrero unsuccessfully argued that since he didn't think he was doing anything illegal, he had no intent (mens rea) to commit the crime. The Court noted that there was a slippery slope, where if they accepted Marrero's excuse, a lot of other people would try the same excuse by purposefully attempting to remain as ignorant of the law as possible. In a dissent, it was argued that Marrero didn't do anything morally wrong, he just violated a Statute while acting in good faith. Therefore there is no reason for society to punish him. See Model Penal Code §2.04. Perhaps Marrero argued this case the wrong way. Instead of arguing that the law was clear but he misinterpreted it, he could have argued that the law was ambiguous and the judges are misinterpreting it. If successfully, Marrero could have invoked the Rule of Lenity, which says that ambiguous Statutes should be interpreted in favor of the defendant.