Alex Adrianson of the Heritage Foundation’s “Insider Online” draws attention to a recent U.S. Supreme Court decision in a North Carolina case.

There are so many criminal laws on the books that virtually anyone can break a law without even intending to do so. Ignorance of the law, they say, is no excuse.

Unless you are a police officer.

The overcriminalization of American society makes victims of citizens by sending them to jail for honest mistakes and acts that nobody could have known were crimes. Now it tramples on the rights of citizens in a new way: The laws are so voluminous that even the police cannot be expected to know all of them, a situation which the Supreme Court now recognizes as grounds for deeming a search reasonable even though it wasn’t lawful.

The case is Heine v. North Carolina and it concerns a North Carolina police officer who stopped a driver because he had only one working brake light and subsequently found cocaine in the car. The problem with the stop was that it is not against the law to have only one working brake light, though the officer thought it was.

The Court decided that since the officer’s mistake was reasonable, so was the search. And that means the evidence (the cocaine) isn’t excluded from a trial. Can citizens avail themselves of the same mistake of law defense? Unfortunately, not yet, as Paul Larkin explains:

The Heien opinion will be read as an endorsement of the common law rule that ignorance of the law is no excuse to a crime. The opinion, however, does not examine what that rule means and how it arose.

The common law did not recognize a mistake of law defense because (1) the defense made no sense in past eras when there were only nine felonies, (2) each felony outlawed obviously immoral and harmful conduct, such as murder, rape and robbery, and (3) each crime required the government to prove that the defendant acted with a “guilty mind” or “evil intent.”

The no-ignorance rule made sense 600 years ago but makes no sense today because (1) there are thousands of crimes, (2) in many cases no reasonable person would have thought that the conduct at issue was a crime, and (3) the prosecution does not have to prove that a person acted with a “guilty mind” or “evil intent” in every case.