Also known as: mistakes of law
Written by attorneys · grounded in primary & secondary sources — see below
A belief that a legal rule has a particular content or effect when in fact it does not. The belief does not relieve liability for trespass to chattels or conversion. In criminal law the belief is generally not a defense but may negate a required mental state or support a defense when the defendant reasonably relied on an official statement of law or the rule was not reasonably made available.
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Michael Miller repossessed a delivery van from a defaulting customer after consulting an outdated statute that he believed permitted self-help repossession without court process. The statute in force actually required judicial process. Michael Miller's mistaken belief about the statute does not relieve him of liability for conversion of the van.
A state trooper stopped Melissa Mills's vehicle after concluding that the single working brake light violated a statute requiring two. The statute actually required only one. The trooper's reasonable mistake of law supplied the reasonable suspicion needed for the stop.
Miguel Mendoza failed to file returns for several years after studying the tax code and concluding that wages were not taxable income. The code treats wages as taxable. Mendoza's sincere but erroneous legal belief negates the willfulness element required for criminal tax evasion.
Symphony Space and Pergola Properties executed a long-term option believing the rule against perpetuities did not apply. The rule invalidated the option. The parties' shared mistake of law did not permit rescission of the underlying transaction.
Mustafa Mahmoud structured bank deposits below reporting thresholds after an attorney advised him that the structuring statute required proof of other illegal activity. The statute contained no such element. Mahmoud's mistake of law negated the willfulness required for conviction.
Melanie Morris possessed a rifle after concluding that a prior conviction did not render the firearm illegal under federal law. The statute treated the conviction as disqualifying. Her mistaken legal belief was admissible to negate the knowledge element of the offense.
A mistake of law negates the required mental state when the offense definition makes legal status part of a material element and the defendant's erroneous belief shows the mental state was absent. Modern codes recognize this defense when the mistake undercuts purpose, knowledge, belief, recklessness, or negligence for that element.
Supporting sources
Yes. When a defendant reasonably relies on an official statement from the body charged with interpreting or enforcing the law and that statement later proves wrong, the resulting belief that conduct is lawful supplies a recognized mistake-of-law defense under modern criminal codes.
…188, 191-193 (CA1 1985), we granted certiorari, 493 U. S. 1068 (1990). II The general rule that ignorance of the law or a mistake of law is no defense to criminal prosecution is deeply rooted in the American legal system. See, e. g. , United States v. Smith , 5 Wheat. 153, 182 (1820) (Livingston, J., dissenting); Barlow…
…into the agreement and. that both parties intended the option to be enforceable. CPLR 3005, however, does not equate all mistakes of law
…of law." Ibid. In reversing the order, Justice Holmes stated the following for the Court: "It certainly is true that mere mistakes of law
…law. See, e. g. , Creighton, supra . Our qualified immunity doctrine applies regardless of whether the officer's error is a mistake of law
…sunset for the dawn. Nothing is more common to mankind than mistakes. Volumes, even libraries have been written on
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A defense arises when the statute or rule was not known to the actor and had not been published or otherwise reasonably made available before the conduct. The Model Penal Code expressly recognizes this exception to the general rule that ignorance of the law is no excuse.
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No. An actor's belief, whether of law or fact and not induced by the other party, that he has possession, immediate possession, or consent does not relieve liability for trespass to chattels or conversion.
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Yes. When a writing fails to conform to the parties' agreement because of a mistake of law as to its legal effect, the writing may be reformed to accord with that agreement under agency and contract principles.
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