Ignorantia juris non excusat or ignorantia legis neminem excusat is a legal principle holding that a person who is unaware of a law may not escape liability for violating that law merely by being unaware of its content. In other words, ignorance of law excuses no one. The presumption is that the public knows all the laws, both state and federal, and a defense of ignorance is not allowed. See, Cheek v. United States, 498 U.S. 192, 199, 111 S.Ct. 604 (1991) Lambert v. California, 355 U.S. 225, 228, 78 S.Ct. 240 (1957)
For instance, say you have terrible allergies which cause nasty itchy eyes and throat to where it feels you cannot take a breath. The legislature on April 1, 2021 bans anyone with a meth-related conviction from possessing pseudoephedrine, a common decongestant medicine (and meth ingredient). One month after the effective date, you were charged with violating the law after purchasing allergy medicine containing the substance. You file a motion to dismiss on grounds that the statute was unconstitutional. Trial court denies your motion and you was convicted at trial. That decision was upheld by the North Carolina Supreme Court. See, State v. Miller, 800 S.E.2d 400 (N.C. 2017). The Miller court specifically rejected Miller’s argument that the legislature had criminalized the otherwise innocent act of possessing a pseudoephedrine product for a subset of felons to which defendant belonged despite the fact that the purchase of such substances by individuals like defendant had been entirely lawful little more than a month earlier and that the State’s failure to provide adequate notice of this change in law constituted a federal due process violation. Citing to prior decisions, the North Carolina Supreme Court held that “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. Based on the notion that the law is definite and knowable, the common law presumed that every person knew the law. This common-law rule has been applied by the Court in numerous cases construing criminal statutes.”
Sounds pretty clear, right? A rule that is deeply rooted in the American legal system should apply to everybody , right? Nope. Courts find cops are above deeply rooted rules in the American legal system. In Heien v. North Carolina, 574 U.S. 54 (2014), (on appeal from a decision in North Carolina)and State v. Houghton, 2015 WI 79 (police officer believed any object dangling from a rear-view mirror automatically violated the state’s law on obstructing a driver’s view), courts have found that a police officer’s reasonable mistake of law can provide the individualized suspicion required by the Fourth Amendment to the United States Constitution to justify a traffic stop.
When it comes time for cops to enforce the law, courts have determined that if the cops ignorance of the law is reasonable, the cops actions will be upheld on judicial review. See, Police mistakes of law, 61 Emory L.J. 69 (2011), (even when you are acting legally, cops can stop you) https://scholarlycommons.law.emory.edu/cgi/viewcontent.cgi?article=1276&context=elj It takes little reflection to see “the fundamental unfairness” of holding citizens to strict compliance with the law “while allowing those entrusted to enforce the law” to interpret and apply the law more flexibly. United States v. Chanthasouxat, 342 F.3d 1271, 1280 (11th Cir. 2003) (internal quotation marks omitted).
Courts have now approved a citizen’s oppression not by lawlessness but by the law.