Ignorance of law consists of the want of knowledge of those laws which it is our du ty to understand, and which every man is presumed to know.
The principle that ignorance of the law is no defence (ignorantia legis nqminem es cusat) is generally recognized. It was a maxim of the Roman law, in which this case was put, to illustrate the distinction between ignorance of ldw and fact :—If the heir is ignorant of the death of his ancestor, he is ignorant of a fact ; but if, being aware of his death, and of his own relationship, he is, nevertheless, ignorant that certain rights have thereby become vested in himself, he is ignorant of the law ; D. 22, 6. 1. See 1 Spence, Eq. Jur. 632. The English rule is that every man is presumed to know the law, subject to certain qualifications with respect to questions of doubtful construction, prac tice, and the like; Broom, Leg. Max. 8th Am. ed. 254 ; 6 Cl. & Fin. 911; 11 Exch. 840. The court will only relieve against a pay ment of money under mistake of law, if there be some equitable ground which ren ders it inequitable that the party who re ceived the money should retain it ; 3 Ch. D. 351. This case is said to "contain probably the best statement . . . of the principles upon which the courts proceed in relieving or declining to relieve on the ground of mis take of law ;" Brett, L. Cas. Mod. Eq. 80. The case itself proceeded upon the ground that an erroneous construction of an instru ment was a mistake of law, and it was so held in several cases ; L. R. 14 Eq. 85; 6 H. L. Cas. 798, 811; but for a dictum, contra, see L. R. 6 H. L. 223, 234; and see also 42 Ch. D. 98 ; [1893] 1 Ch. 101, 111. The same general rule is recognized by American'courts. Tiglao v. Insular Government, 215 U. S. 410, 30 Sup. Ct. 129, 54 L. Ed. 257; though earlier cases indicate hesitation on the part of the courts before it was definitely settled. It was said in an early case that whether mon ey paid through ignorance of the law can be recovered back, Is a question much vexed and involved in no inconsiderable perplexity ; Haven v. Foster, 9 Pick. (Mass.) 112, 19 Am. Dec. 353; and that when one makes a prom ise as an "expression of an opinion of what he should be obliged to, allow, rather than of what he was willing to allow, and being un der a mistake of his right, he is not bound by it ;" Levy v. Bank, 1 Binn. (Pa.) 27, 37. But it may be considered as well established that money paid with full knowledge of all the facts and circumstances cannot be recov ered back upon the ground that the party supposed he was bound in law to pay it, when in truth he was not ; Real Estate Sav ing Institution v. Linder, 74' Pa. 371; Hol lingsworth v. Stone, 90 Ind. 244; Arnold v.
Banking Co., 50 Ga. 304 (practically overrul ing Collier v. Perkerson, 31 Ga. 117; Eaton v. Eaton, 35 N. J. L. 290; Mutual Savings Institution v. Enslin, 46 Mo. 200 ; Gross v. Parrott, 16 Cal. 143; Johnson v. McGin ness, 1 Or. 292 ; contra, City of Coving ton v. Powell, 2 Mete. (Ky.) 226 ; and a person cannot be permitted to disavow or avoid the operation of an agreement en tered into with a full knowledge of the facts, on the ground of ignorance of the legal consequences which flow from those facts ; Shotwell v. Murray, 1 Johns. Ch. (N. Y.) 512, 516. See 1 V. & B. 23, 30; Osburn v. Throckmorton, 90 Va. 311, 18 S. E. 285; Gefken v. Graef, 77 Ga. 340. Ignorance of one's legal right does not take a case out of the rule of equitable estoppel *here one en courages a purchaser to take land from one having a color of title when otherwise he would be entitled to interpose an equitable bar to the latter's legal title ; Butts v. Cuth bertson, 6 Ga. 166.
It has been said that whatever rule may prevail elsewhere, in the equity courts of the U. S., there is no relief from a mistake of law alone ; Allen v. Galloway, 30 Fed. 466 ; Upton v. Tribilcock, 91 U. S. 50, 51, 23 L. Ed. 203; Lamborn v. Dickinson County, 97 U. S. 185, 24 L. Ed. 926 ; U. S. v. Ames, 99 U. S. 40, 25 L. Ed. 295 ; Utermeble v. Nor ment, 197 U. S. 40, 25 Sup. Ct. 291, 49 L. Ed. 655, 3 Ann. Cas. 520. But there is to be found by careful reading of the Federal cas es the same disposition apparent in English cases, to avoid the establishment of an in flexible rule which shall preclude relief if there be any other circumstances or any fea ture of the case itself to warrant it. In Hunt v. Ennis, 2 Mas. 244, Fed. Cas. No. 6,889, Hunt v. Rousmanier's Adm'rs, 8 Wheat. (U. S.) 174, 5 L. Ed. 589, and Hunt v. Rhodes, 1 Pet. (U. S.) 1, 7 L. Ed. 27, the United States supreme court said, where an instrument is executed by the parties, which contains a mistake of the draughtsman either of fact or law it may be reformed, but not when it was executed in the form agreed upon under a misapprehension of the law as to its na ture or effect ; that a mistake of law is not a ground for reforming a deed and the ex ceptions are both few and peculiar, but it was not the intention to lay down a rule that there might not be relief against a plain mistake arising from ignorance of law ; and in a later case the court quoted this expres sion with approval and also the declaration from 1 Sto. Eq. Jur. Redf. ed. § 138 e, that established misapprehension of the law does afford a basis for relief resting on discretion and to be exercised only in flagrant and un questionable cases ; Snell v.. Ins. Co., 98 U. S. 85, 91, 25 L. Ed. 52.