What does the old legal maxim “ignorance of the law is no excuse” really mean?1 Since federal, state, and local governments pass more laws than any individual can know and remember, does “ignorance of the law is no excuse” apply to law enforcement officers as well as civilians? Mistakes of fact can happen, but what happens when a law enforcement officer makes a mistake of law? Chief Justice Roberts delivered the U.S. Supreme Court’s opinion in Heien v. North Carolina on December 15, 2014, in which he held that an officer can have a reasonable mistake of law that gives rise to reasonable suspicion necessary to uphold a seizure under the Fourth Amendment
