Ignorantia juris non excusat, or “ignorance of the law is no excuse,” is according to one waggish law professor “almost the only knowledge of law possessed by many people.” This doctrine, which helps the justice system avoid having to make the preposterous presumption that everyone knows the law, is more than a little misleading. Anyone who’s suffered through a criminal law course, although probably still too confused to clearly explain the assorted situations of “mistake of fact” and “mistake of law,” could hopefully tell you that ignorance of the law might, in fact, mean an acquittal. Moreover, scholarship in the last 25 years has uncovered that most of the doctrine’s authority never was—it was all the product of sloppy legal research.

Indeed, a good deal of the modern reliance on ignorantia legis neminem excusat (an alternative expression of the doctrine) came from Sir William Blackstone, a English judge who in the 1760s wrote a famous treatise on the common law. For the authority of the proposition Blackstone cited Sir Matthew Hale, Lord Chief Justice of England and Wales in the 1600s, who in turn cited Brett v. Rigden, 75 Eng. Rep. 516, 520 (1568). It turns out, though, that Brett v. Rigden is some random civil case about a will where one of the barristers happened to mention—in one part of his (reprinted) argument—that “every one shall be presumed to know the law.” And, in any event, that argument lost. Blackstone’s other authority for the doctrine, Roman law, is similarly unsupportive. The Romans expressed the doctrine as error juris nocet error facti non nocet but only applied it to members of the public who could reasonably be expected to know the law, and never applied it in criminal cases. All of this cite-checking on Blackstone was done by Paul Matthews, a law professor at King’s College London and author of Ignorance of the Law Is No Excuse?, 3 Legal Stud. 174 (1983).

From the U.S., you’ll find a sizable gang of law review articles on mistake/ignorance of law, and many of them report that the doctrine is eroding. In Cheek v. United States, 498 U.S. 192 (1991), for instance, the U.S. Supreme Court made it clear that the federal tax laws can be so difficult to understand that Congress couldn’t have meant for people’s ignorance of them to be inexcusable. Thus, in that case, even a guy who claimed that he didn’t know wages were income was allowed to seek acquittal based on his purported misunderstanding. In other areas, however, the Court has not been so merciful. Like in Federal Crop Insurance Company v. Merrill, 332 U.S. 380 (1947), where a federal agent misrepresented (perhaps innocently) to some Idaho farmers what crops were covered by the federal crop insurance they were buying. Then, when drought destroyed the farmers’ crop, the federal agency was happy to tell them, oh sorry, they’re not covered; and the Supreme Court of the United States was happy to tell them, oh sorry, you should have been reading the Federal Register. As I’m sure you know (because you are held by law to this knowledge), the Federal Register is a daily publication of the federal government containing the latest federal rules and regulations. So far this year, there have been over 58,000 pages of Federal Register. As Justice Robert Jackson said, dissenting from the Court’s decision in Merrill:

To my mind, it is an absurdity to hold that every farmer who insures his crops knows what the Federal Register contains or even knows that there is such a publication. If he were to peruse this voluminous and dull publication as it is issued from time to time in order to make sure whether anything has been promulgated that affects his rights, he would never need crop insurance, for he would never get time to plant any crops.

Jackson called for a rule that “recognized the practicalities of business.” I wonder, though, why nearly nobody sees any of this as a constitutional concern. There is, after all, a growing body of law making it almost a constitutional violation to deny a non-English speaker an interpreter in court. And at least one federal court has taken note of how difficult it is for even educated English speakers to understand legal jargon (see Seltzer v. Foley, 502 F. Supp. 600, 605 (S.D.N.Y. 1980), where the court notes that it may be “necessary to have a minimum of 14 years of education (equivalent to 2 years of college) to understand what goes on in a criminal trial” and even more for a civil trial).

But, I suppose I better stop wasting my time and get to reading today’s Federal Register.