An exception has been made to the rule denying relief for mistake of the law governing a situation prior to the bargain, where the mistake relates to the private rights of the parties as distinguished from a mistake as to the general law. Lord West-bury, in a leading English case,49 took this distinction. "It is said, 'Ignorantia juris hand excusat;' but in that maxim the word 'jus' is used in the sense of denoting general law, the ordinary law of the country. But when the word 'jus' is used in the sense of denoting a private right, that maxim has no application. Private right of ownership is a matter of fact; it may be the result also of matter of law; but if parties contract under a mutual mistake and misapprehension as to their relative and respective rights, the result is, that that agreement is hable to be set aside as having proceeded upon a common mistake."50
47 Quoted with approval in the dissenting opinion in Atherton v. Roche, 192 I11. 262, 265, 61 N. E. 357, 55 L. R. A. 501, with the further citation to the same effect of Coleman v. Coleman, 153 la. 543, 133 N. W. 755; Wisconsin Marine, etc., Bank v. Mann, 100 Wis. 596, 76 N. W. 777. In the latter case the court said at p. 619: "Many cases may be cited to support the contention made by appellant's counsel, that a mistake of law is not remediable in equity, but they do not fit this case. They refer to a mistake of law in the making of the verbal contract as distinguished from a mere mistake in reducing the contract to writing through some misapprehension of the legal meaning of the language used. The rule applies where the contract is written so as to express the agreement as understood, though the understanding were wrong through ignorance of law; it does not apply where the contract is fully understood but is incorrectly expressed in the writing through ignorance as to the legal import of the language selected by the parties for that purpose.11
48 Daniels v. Tearney, 102 U. S. 415, 26 L. Ed. 187; People's Lumber Co. v. Gillard, 136 Cal. 55, 68 Pac. 576; State ex rel. Cantwell v. Stark, 75 Mo. 566; United States Fidelity, etc., Co. v. Ettenheimer, 70 Neb. 144, 147, 97 N. W. 227, 99 N. W. 652, 113 Am. St. Rep. 783. See also Boese v. King, 106 U. S. 379, 27 L. Ed. 760, 2 Sup. Ct. 765. Cf. Shaughnessy v. American Surety Co., 138 Cal. 543, 69 Pac. 250, 71 Pac. 701; Cassel v. Scott, 17 Ind. 514; Brookman v. Hamill, 43 N. Y. 554, 3 Am. Rep. 731; Poole v. Kermit, 59 N. Y. 554; Love v. McCoy, 81 W. Va. 478, 94 S. E. 954.
49 Cooper v. Phibbs, L. R. 2 H. L. 149.
50 See also to similar effect, Beau-champ v. Winn, LR.6H. L.223, 234; In re Oliver's Settlement,  1Ch. 191; State v. Paup, 13 Ark. 129, 56 Am. Dec. 303; Hannah v. Steinman, 159 Cal. 142, 112 Pac. 1094; Stoeckle v. Rosenheim, 10 Del. Ch. 195, 87 Atl. 1006; Gefken v. Graef, 77 Ga. 340; Bonney v. Stoughton, 122 I11. 536, 544, 13 N. E. 833; Baker v. Massey, 50 la. 399; Lewis v. Mote, 140 la. 698,119 N. W. 152; Livingstone v. Murphy, 187 Maes. 315, 72 N. E. 1012; Reggio v. Warren, 207 Mass. 525, 534, 93 N. E. 805, 32 L. R. A. (N. S) 340; Renard v. Clink, 91 Mich. 1, 51 N. W. 692, 30 Am. St. Rep. 458; Alabama, etc, Ry. Co. v. Jones, 73 Miss. 110, 19 So. 105, 55 Am. St. Rep. 488; Hoy v. Hoy, 93 Miss. 732, 48 So. 903, 25 L. R. A. (N. S.) 182; Griffith v. Town-ley, 69 Mo. 13, 33 Am. Rep. 476; Blair v. Chicago, etc., R. Co., 89 Mo. 383, 1 S. W. 350; Mclntyre v. Casey (Mo.), 182 S. W. 966; Williams v. Union Bank, 9 Heisk. 441; Cook v. Sumner Spinning, etc., Co., 1 Sneed, 698; Toland v. Corey, 6 Utah, 392, 24 Pac. 190; Burton v. Haden, 108 Va. 61, 60 S. E. 736, 15 L. R. A. (N. S.) 1038; Waggoner v. Waggoner, I11 Va. 325, 68 S. E. 990, 30 L. R. A. (N. S.) 644. See also Tarboz v. Tarbox, I11 Me. 374, 89 Atl. 194. But see Thomas v. Chicago, 55 I11. 403; Kirkland v. Edenborn, 140 La. 669, 73 So. 719; Clark v. Lehigh, etc., Coal Co., 250 Pa. 304, 312, 95 Atl 462. In the case last cited the court said: "It is conceded that if the lessee was induced to enter into the lease by a mistake it was one of law and not of fact. The land in question is what was known as a 'Commissioner's Road,' and the alleged mistake was in construing the defendant's title to the adjacent land as extending to the edge of the road and not to its center. As pointed out above, there could not have been a mistake of fact, as the title of each party was of record and hence the parties had all the facts before them when the lease was made. It is not alleged that the lessee was induced to enter into the lease by any fraud, misrepresentation, concealment of facts, or other inequitable conduct on the part of the lessor. There are no special circumstances or facts in the case, disclosed by the record, to induce a chancellor to give relief to the complaining party. As suggested above, the contract may have been advantageous to the lessee company notwithstanding it was the owner of the fourth piece of coal. We are, therefore, dealing here with a mistake of law, pure and simple, unaided by any equitable consideration which should move a chancellor to grant relief. Under these circumstances, it is settled that equity will not relieve against a mistake of law." Citing earlier Pennsylvania cases and Utermehle v. Norment, 197 U. S. 40, 49 L. Ed. 655; Midland Great Western Ry. Co. v. Johnson, 6E L, Gas. 798.
The only merit of this distinction between private right and general law is that it enables a court of equity to give relief in a majority of cases where the parties to a transaction assumed as a basis for it a certain legal situation. Almost always such an assumption is based on a rule of law affecting the relative rights of the parties. Their mistake may be ignorance of a most fundamental principle of general law, but if the effect of that general rule is to vary their private rights, they come within the exception.
In England at least, and perhaps in the United States, this exception of mistake as to private rights, though available in equitable proceedings, is not made to the general denial of the right to recover money paid under a mistake of law.61 There seems no logical reason for distinguishing in this particular between a bill to reform or rescind and an action for money had and received.
52 In Stanley Bra., Ltd., v. Corporation of Nuneaton, 108 Law Times (N.S.) 986, 992, it was said: "I think, however, as Bailhaehe, J., decided otherwise, and decided upon the ground that in his view it was a mistake of fact and not of law, that I ought to say a word upon that. His attention was directed to Earl Beau-champ's case (Earl Beauchamp v. Winn, 6 E. & I. App. 234), which is a case in which the claimant was ordered relief from the obligation of an agreement upon the ground that the specifio private rights affecting the subject-matter of that agreement had been mistakenly construed by the plaintiff in the action. His attention was not drawn to the proposition laid down in Rogers v. lngham,| by Lord Mellish (36 L. T. Rep. 677, 3 Ch. Div. 367), that such a doctrine has never been applied to a claim for the return of money paid under a mistake of fact. The equity in the latter case is the supposed equity that it is unusual for the defendant to keep money which the plaintiff voluntarily gave him, but under a mistake which was not common to the two; the equity, whatever else may be said of it, is at any rate not the same equity as that which is put into force when the relief by way of rescission by the act of the court of an obligation which is entered into is sought upon the ground that the contract had been entered into or the conveyance executed under a misapprehension as to one of the parties existing private rights. Even so a passage in the case of Midland Great Western Railway v. Johnson (6 H. L. Cas. 811), and in this court in Wilding v. Sanderson (77 L. T. Rep. 57; (1897) 2 Ch. at p. 660), ought to be borne in mind. The passage by Lord Chelmsford in the former case is:' It must be a mistake not in matter of law, but a mistake of facts. The construction of a contract is clearly matter of law; and if a party acts upon a mistaken view of his rights under a contract, he is no more entitled to relief in equity than he would be in law.' The passage in the other judgment is: 'A written contract cannot be impeached simply because one of the parties to it put an erroneous construction on the words in which the contract is expressed.' There must be some case either of error induced by misrepresentation of the opposite party or error as to the subject-matter with which the contract purports to deal. I think, therefore, the mistake in question was not a mistake of fact but of law."