Opinion of the Court. 254 U. S. and carry out the messenger's agreement, to execute a sufficient release of all claims on account of the injuries received, and to abstain from enforcing the judgment. General relief also is prayed. Taylor challenged the bill by a demurrer, which was overruled, and after a hearing in due course the express company prevailed. On appeal to the Circuit Court of Appeals that decree was reversed and the suit remanded because in that court's opinion the bill did not show that Taylor was not in the employ of the railroad company or that he was solely in the employ of the express company. 220 Fed. Rep. 796. After the mandate was received, Taylor, conceiving that the decision of the Circuit Court of Appeals fully disposed of the merits and was final, requested the District Court to enter a decree dismissing the bill, and the express company requested leave to amend the bill by correcting the defect pointed out by the Circuit Court of Appeals. Taylor's request was denied and that of the express company was granted. The bill was accordingly amended so as to show that Taylor was not in the employ of the railroad company, but was on the train solely in virtue of his employment by the express company, and that in his declaration in the action against the railroad company he did not claim or allege any employment by that company, but, on the contrary, claimed and alleged that it permitted him to be on the train because he was accompanying the express matter as the express company's employee. Taylor then filed a new answer, and on a further hearing a decree for the express company was entered. By it the District Court found that the allegations of the bill, with its supplement and amendment, were all true; declared that the institution of the action against the railroad company and its prosecution to judgment constituted a violation of the messenger's agreement and a legal fraud on the express company; directed Taylor to carry out and perform the messenger's 175. Opinion of the Court. agreement and to execute, within a fixed time, an appropriate instrument releasing the express company and the railroad company from all claims for damages on account of his injuries, and enjoined him from collecting or attempting to collect the judgment against the railroad company. On a further appeal to the Circuit Court of Appeals that decree was reversed with directions to dismiss the bill. 249 Fed. Rep. 109. A writ of certiorari was then granted by this court. On the second appeal the Circuit Court of Appeals put its decision entirely on the ground that the express company was a "common carrier by railroad" within the meaning of the Employers' Liability Act of April 22, 1908, c. 149, 35 Stat. 65, and therefore under § 5 of the act the messenger's agreement was void. Taylor advanced that and other grounds in asking a reversal, but the court did not discuss the other grounds. All are pressed on our attention, and we take them up in what seems the natural order. 1. It is urged that the decision of the Circuit Court of Appeals on the first appeal was final in that it disposed of all questions in the suit and left nothing open to the District Court but to dismiss the bill. Had this been so, the Circuit Court of Appeals on the second appeal hardly would have failed to enforce its prior decision. But that decision did not go as far as is claimed. It turned on the sufficiency of the bill, and on that alone. The District Court had held the bill sufficient when challenged by a demurrer. The Circuit Court of Appeals held it insufficient, and for that reason reversed the decree and remanded the suit. Had the District Court taken that view when acting on the demurrer, it undoubtedly could, and probably would, have allowed an amendment curing the defect. Could it not equally allow the amendment after the Circuit Court of Appeals pointed out the defect and remanded the suit? It, of course, was bound to give effect to the decision and Opinion of the Court. 254 U.S. mandate of the Circuit Court of Appeals; but that court did not order the bill dismissed nor give any direction even impliedly making against the amendment. All that was disposed of was the matter of the sufficiency of the bill. And recognition of this is found in the last opinion of the Circuit Court of Appeals, where it is said that the first reversal was "based upon the insufficiency of the pleadings." We think the decision on the first appeal was not final and that the District Court was left free, in the exercise of its discretion, to permit the amendment. Equity Rules, Nos. 19 and 28; In re Sanford Fork & Tool Co., 160 U. S. 247, 258–259; Mutual Life Insurance Co. v. Hill, 193 U. S. 551, 553; Smith v. Adams, 130 U. S. 167, 177. It appears that in denying a petition for a rehearing on the first appeal the Circuit Court of Appeals refused to direct the allowance of the amendment; but this signifies nothing more than that no occasion was perceived for controlling the District Court's discretion in the matter. 2. Section 265, Judicial Code, formerly § 720, Rev. Stats., provides that "The writ of injunction shall not be granted by any court of the United States to stay proceedings in any court of a State, except in cases where such injunction may be authorized by any law relating to proceedings in bankruptcy"; and this is relied on as showing that the District Court could not entertain the suit. That court held the provision not applicable, and the Circuit Court of Appeals said nothing on the subject on either appeal, possibly because in a similar case it had held the provision without application. Is the suit one to stay proceedings in a state court in the sense of that provision? If it is, the District Court erred in not dismissing the bill on that ground. Haines v. Carpenter, 91 U. S. 254; Dial v. Reynolds, 96 U. S. 340; United States v. Parkhurst-Davis Co., 176 U. S. 317. If it is not, the court rightly entertained the suit and proceeded to an adjudication of the merits, for the citizenship of the parties and the amount in controversy were within the jurisdictional requirements. The provision has been in force more than a century and often has been considered by this court. As the decisions show, it is intended to give effect to a familiar rule of comity and like that rule is limited in its field of operation. Within that field it tends to prevent unseemly interference with the orderly disposal of litigation in the state courts and is salutary; but to carry it beyond that field would materially hamper the federal courts in the discharge of duties otherwise plainly cast upon them by the Constitution and the laws of Congress, which of course is not contemplated. As with many other statutory provisions, this one is designed to be in accord with, and not antagonistic to, our dual system of courts. In recognition of this it has come to be settled by repeated decisions and in actual practice that, where the elements of federal and equity jurisdiction are present, the provision does not prevent the federal courts from enjoining the institution in the state courts of proceedings to enforce local statutes which are repugnant to the Constitution of the United States, Ex parte Young, 209 U. S. 123; Truax v. Raich, 239 U. S. 33; Missouri v. Chicago, Burlington & Quincy R. R. Co., 241 U. S. 533, 538, 543; or prevent them from maintaining and protecting their own jurisdiction, properly acquired and still subsisting, by enjoining attempts to frustrate, defeat or impair it through proceedings in the state courts, French v. Hay, 22 Wall. 250; Julian v. Central Trust Co., 193 U. S. 93, 112; Chesapeake & Ohio Ry. Co. v. McCabe, 213 U. S. 207, 219; Looney v. Eastern Texas R. R. Co., 247 U. S. 214, 221; or prevent them from depriving a party, by means of an injunction, of the benefit of a judgment obtained in a state court in circumstances where its enforcement will be contrary to recognized principles of equity and the standards of good conscience, Marshall v. Holmes, 141 U. S. 589; Ex parte Simon, 208 U. S. 144; Opinion of the Court. 254 U.S. Simon v. Southern Ry. Co., 236 U. S. 115; Public Service Co. v. Corboy, 250 U. S. 153, 160; National Surety Co. v. State Bank of Humboldt, 120 Fed. Rep. 593. Marshall v. Holmes, just cited, was a suit in equity to enjoin one who had obtained judgments in a state court from enforcing them, that relief being sought on the ground that they were secured by fraud which was not discovered until after they were rendered; and the question distinctly presented was whether the suit was one which the Circuit Court of the United States could entertain and decide, the requisite diversity of citizenship and amount in dispute being present. This court,--after adverting to prior decisions stating the familiar doctrine that "any fact which clearly proves it to be against conscience to execute a judgment, and of which the injured party could not have availed himself in a court of law, or of which he might have availed himself at law, but was prevented by fraud or accident, unmixed with any fault or negligence in himself or his agents, will justify an application to a court of chancery," and also showing that such a suit is not one to review or revise the action of the court rendering the judgment, but is a new and independent suit for equitable relief,—answered the question by saying: "These authorities would seem to place beyond question the jurisdiction of the Circuit Court to take cognizance of the present suit, which is none the less an original, independent suit, because it relates to judgments obtained in the court of another jurisdiction. While it cannot require the state court itself to set aside or vacate the judgments in question, it may, as between the parties before it, if the facts justify such relief, adjudge that Mayer shall not enjoy the inequitable advantage obtained by his judgments. A decree to that effect would operate directly upon him, and would not contravene that provision of the statute prohibiting a court of the United States from granting a writ of injunction to stay proceedings in a |