There is no portion of the law of mistake more troublesome than that relating to mistake of law. It is impossible to coordinate the cases so as to produce satisfactory results, because the rule itself distinguishing mistake of law from mistake of fact is founded on no sound principle. Ignorance of law does not excuse one who has violated a prohibition of the law from the penalties that the law imposes. This is a necessary rule not only of the law of crimes and torts, but it is generally true also that a contract forbidden by law, or a contract to do an act forbidden by law, is none the less unenforceable because the parties were ignorant of the law or made a mistake in regard to it, though this principle is not without exception.7 Such a rule is necessary to enforce the orders of society; but the only bearing that it has on the reformation or rescission of contracts, or the recovery of payments made under a mistake is when the contract or payment is tainted with illegality. Prior to the nineteenth century no indication of a distinction between mistake of law and mistake of fact is to be found, and indeed not only are there early authorities, both at law 8 and in equity,9 for the allowance of relief in cases of mistake of law, but a decision by Lord Mansfield only a few years before the close of the eighteenth century 10 is to the same effect. Yet at the beginning of the nineteenth century in a case before Lord Ellenborough, who was trained in criminal trials, it was held that mistake of law afforded no ground for quasi-contractual recovery,11 and though within ten years the same judge held a mistake of law sufficient ground for disregarding the cancellation of a deed,12

6 Hayes v. Penn. Mut. L. Ins. Co., 228 Mass. 122, 117 N. E. 191; Stett-heimer v. Killip, 75 N. Y. 282; Susquehanna Ins. Co. v. Swank, 102 Pa. 17; Bible v. Centre Hall Borough, 19 Pa. Super. 136; Diman v. Providence, etc., R. Co., 5 R. I. 130. See also Star Glass Co. v. Longley, 64 Ga. 576; Phillip v. Gallant, 62 N. Y. 256.

7 See infra, Sec. 1632.

8 Hewer v. Bartholomew, Cro. Elk. 614; Bonnel v. Foulke, 2 Sid. 4.

9 Turner v. Turner, 2 Rep. Ch. 154; Lansdown v. Lansdown, 2 Jac. & W. 205, n.

10 Bize v. Dickason, 1 T. R. 285.

11 Bilbie v. Lumley, 2 East, 469.

12 Perrott v. Perrott, 14 East, 423.

his earlier statement became generally accepted both at law and in equity. But the injustice of some of the results produced thereby has led to an increasing number of exceptions which have to a considerable extent destroyed the rule, and often make it difficult to determine in what cases it may still be thought applicable. The only way apparent for the law on the subject to obtain uniformity and certainty is by the gradual broadening of these exceptions until they so far coalesce that courts will venture to put mistakes of law and of fact on the same footing.