opinion: VENDO CO. v. LEKTRO-VEND CORP. et al.
  No. 76-156.
  Argued January 19, 1977
  Decided June 29, 1977
  RehNQUist, J., announced the Court’s judgment and delivered an opinion, in which Steivart and Powell, JJ., joined. Blackmun, J., filed an opinion concurring in the result, in which Burgee, C. J., joined, post, p. 643. Stevens, J., filed a dissenting opinion, in which Brennan, White, and Marshall, JJ., joined, post, p. 645.
  Earl E. Pollock argued the cause for petitioner. With him on the briefs was Lambert M. Ochsenschlager.
  Barnabas F. Sears argued the cause for respondents. With him on the brief were James E. S. Baker and Thomas L. Brejcha, Jr.
  Mr. Justice Rehnquist
  announced the judgment of the Court and delivered an opinion in which Mr. Justice Stewart and Mr. Justice Powell join.
  I
  After nine years of litigation in the Illinois state courts, the Supreme Court of Illinois affirmed a judgment in favor of petitioner and against respondents in the amount of $7,363,500. Shortly afterwards the United States District Court for the Northern District of Illinois enjoined, at the behest of respondents, state proceedings to collect the judgment. 403 F. Supp. 527 (1975). The order of the United States District Court was affirmed by the Court of Appeals for the Seventh Circuit, 545 F. 2d 1050 (1976), and we granted certiorari to consider the important question of the relationship between state and federal courts which such an injunction raises. 429 U. S. 815 (1976)
  The Illinois state-court litigation arose out of commercial dealings between petitioner and respondents. In 1959 petitioner Vendo Co., a vending machine manufacturer located in Kansas City, Mo., acquired most of the assets of Stoner Manufacturing, which was thereupon reorganized as respondent Stoner Investments, Inc. Respondent Harry H. Stoner and members of his family owned all of the stock of Stoner Manufacturing, and that of Stoner Investments. Stoner Manufacturing had engaged in the manufacture of vending machines which dispensed candy, and as a part of the acquisition agreement it undertook to refrain from owning or managing any business engaged in the manufacture or sale of vending machines. Pursuant to an employment contract, respondent Harry Stoner was employed by petitioner as a consultant for five years at a salary of $50,000, and he agreed that during the term of his contract and for five years thereafter he would not compete with petitioner in the business of manufacturing vending machines.
  In 1965, petitioner sued respondents in state court for breach of these noncompetition covenants. Shortly thereafter, respondents sued petitioner in the United States District Court for the Northern District of Illinois, complaining that petitioner had violated §§ 1 and 2 of the Sherman Act, 15 U. S. C. §§ 1 and 2. Respondents alleged that the covenants against competition were unreasonable restraints of trade because they were not reasonably limited as to time and place, and that the purpose of petitioner's state-court lawsuit was to “unlawfully harass” respondents and to “eliminate the competition” of respondents. App. 22, 25.
  Respondents set up this federal antitrust claim as an affirmative defense to petitioner’s state-court suit. Id., at 31-32. However, prior to any ruling by the state courts on the merits of this defense, respondents voluntarily withdrew it. Id., at 82.
  The state-court litigation ran its protracted course, including two trials, two appeals to the State Appellate Court, and an appeal to the Supreme Court of Illinois. In September 1974, the latter court affirmed a judgment in favor of petitioner and against respondents in an amount exceeding $7 million. Vendo Co. v. Stoner, 58 Ill. 2d 289, 321 N. E. 2d 1. The Supreme Court of Illinois predicated its judgment on its holding that Stoner had breached a fiduciary duty owed to petitioner, rather than upon any breach of the noncompetitive covenants. This Court denied respondents' petition for a writ of certiorari. 420 U. S. 975 (1975).
  During the entire nine-year course of the state-court litigation, respondents’ antitrust sdit in the District Court was, in the words of the Court of Appeals, allowed to lie “dormant.” 545 F. 2d, at 1055. But the day after a Circuit Justice of this Court had denied a stay of execution pending petition for certiorari to the Supreme Court of Illinois, respondents moved in the District Court for a preliminary injunction against collection of the Illinois judgment. The District Court in due course granted this motion.
  That court found that it “appear [ed] that the [noncom-petition] covenants . . . were overly broad,” 403 F. Supp., at 533, and that there was “persuasive evidence that Vendors activities in its litigation against the Stoner interests in Illinois state court were not a genuine attempt to use the adjudicative process legitimately.” Id., at 534-535. . Recognizing that there is a “paucity of authority” on the issue, id., at 536, the District Court held that the injunctive-relief provision of the Clayton Act, 15 U. S. C. § 26, constitutes an express exception to 28 U. S. C. § 2283, the “Anti-Injunction Act.” The court further found that collection efforts would eliminate two of the three plaintiffs and thus that the injunction was necessary to protect the jurisdiction of the court, within the meaning of that exception to § 2283.
  The Court of Appeals affirmed, finding that § 16 of the Clayton Act was an express exception to § 2283. The court did not reach the issue of whether an injunction was necessary to protect the jurisdiction of the District Court.
  In this Court, petitioner renews its contention that principles of equity, comity, and federalism, as well as the Anti-Injunction Act, barred the issuance of the injunction by the District Court. Petitioner also asserts in its brief on the merits that the United States District Court was required to give full faith and credit to the judgment entered by the Illinois courts. Because we agree with petitioner that the District Court’s order violated the Anti-Injunction Act, we reach none of its other contentions.
  Ill
  The Anti-Injunction Act, 28 U. S. C. §2283, provides:
  “A court of the United States may not grant an injunction to stay proceedings in a State court except as expressly authorized by Act of Congress, or where necessary in aid of its jurisdiction,' or to protect or effectuate its judgments."
  The origins and development of the present Act, and of the statutes which preceded it, have been amply described in our prior opinions and need not be restated here. The most recent of these opinions are Mitchum v. Foster, 407 U. S. 225 (1972), and Atlantic Coast Line R. Co. v. Locomotive Engineers, 398 U. S. 281 (1970). Suffice it to say that the Act is an absolute prohibition against any injunction of any state-court proceedings, unless the injunction falls within one of the three specifically defined exceptions in the Act. The Act’s purpose is to forestall the inevitable friction between the state and federal courts that ensues from the injunction of state judicial proceedings by a federal court. Oklahoma Packing Co. v. Oklahoma Gas & Electric Co., 309 U. S. 4, 9 (1940). Respondents’ principal contention is that, as the Court of Appeals held, § 16 of the Clayton Act, which authorizes a private action to redress violations of the antitrust laws, comes within the “expressly authorized” exception to § 2283.
  We test this proposition mindful of our admonition that
  “[a]ny doubts as to the propriety of a federal injunction against state court proceedings should be resolved in favor of permitting the state courts to proceed in an orderly fashion to finally determine the controversy.” Atlantic Coast Line R. Co., supra, at 297.
  This cautious approach is mandated by the “explicit wording of § 2283” and the “fundamental principle of a dual system of courts.” Ibid. We have no occasion to construe the section more broadly:
  “[It is] clear beyond cavil that the prohibition is not to be whittled away by judicial improvisation.” Clothing Workers v. Richman Bros. Co., 348 U. S. 511, 514 (1955).
  Our inquiry, of course, begins with the language of § 16 of the Clayton Act, which is the statute claimed to “expressly authorize” the injunction issued here. It provides, in pertinent part:
  “[A]ny person . . . shall be entitled to sue for and have injunctive relief, in any court of the United States having jurisdiction over the parties, against threatened loss or damage by a violation of the antitrust laws . . . when and under the same conditions and principles as injunctive relief against threatened conduct that will cause loss or damage is granted by courts of equity, under the rules governing such proceedings . . . .” 38 Stat. 737, 15 U. S. C. § 26.
  On its face, the language merely authorizes private injunctive relief for antitrust violations. Not only does the statute not mention § 2283 or the enjoining of state-court proceedings, but the granting of injunctive relief under § 16 is by the terms of that section limited to “the same conditions and principles” employed by courts of equity, and by “the rules governing such proceedings.” In 1793 the predecessor to § 2283 was enacted specifically to limit the general equity powers of a federal court. Smith v. Apple, 264 U. S. 274, 279 (1924) ; Toucey v. New York Life Ins. Co., 314 U. S. 118, 130 n. 2 (1941). When § 16 was enacted in 1914 the bar of the Anti-Injunction Act had long constrained the equitable power of federal courts to issue injunctions. Thus, on its face, § 16 is far from an express exception to the Anti-Injunction Act, and may be fairly read as virtually incorporating the prohibitions of the Anti-Injunction Act with restrictive language not found, for example, in 42 U. S. C. § 1983. See discussion of Mitchum v. Foster, infra.
  Respondents rely, as did the Court of Appeals and the District Court, on the following language from Mitchum:
  . . [I]t is clear that, in order to qualify as an ‘expressly authorized' exception to the anti-injunction statute, an Act of Congress must have created a specific and uniquely federal right or remedy, enforceable in a federal court of equity, that could be frustrated if the federal court were not empowered to enjoin a state court proceeding. This is not to say that in order to come within the exception an Act of Congress must, on its face and in every one of its provisions, be totally incompatible with the prohibition of the anti-injunction statute. The test, rather, is whether an Act of Congress, clearly creating a federal right or remedy enforceable in a federal court of equity, could be given its intended scope only by the stay of a state court proceeding.” 407 U. S., at 237-238. (Emphasis added, footnote omitted.)
  But we think it is clear that neither this language from Mitchum nor Mitchum’s ratio decidendi supports the result contended for by respondents.
  The private action for damages conferred by the Clayton Act is a “uniquely federal right or remedy,” in that actions based upon it may be brought only in the federal courts. See General Investment Co. v. Lake Shore & Mich. So. R. Co., 260 U. S. 261, 287 (1922). It thus meets the first part of the test laid down in the language quoted from Mitchum.
  But that authorization for private actions does not meet the second part of the Mitchum test; it is not an “Act of Congress . . . [which] could be given its intended scope only by the stay of a state court proceeding,” 407 U. S., at 238. Crucial to our determination in Mitchum that 42 U. S. C.
  § 1983 fulfilled this requirement — but wholly lacking here— was our recognition that one of the clear congressional concerns underlying the enactment of § 1983 was the possibility that state courts, as well as other branches of state government, might be used as instruments to deny citizens their rights under the Federal Constitution. This determination was based on our review of the legislative history of § 1983; similar review of the legislative history underlying § 16 demonstrates that that section does not meet this aspect of the Mitchum test.
  Section 1983 on its face, of course, contains no reference to § 2283, nor does it expressly authorize injunctions against state-court proceedings. But, as Mitchum recognized, such language need not invariably be present in order for a statute to come within the “expressly authorized” exception if there exists sufficient evidence in the legislative history demonstrating that Congress recognized and intended the statute to authorize injunction of state-court proceedings. In Part IY of our opinion in Mitchum we examined in extenso the purpose and legislative history underlying § 1983, originally § 1 of the Civil Rights Act of 1871. We recounted in detail that statute’s history which made it abundantly clear that by its enactment Congress demonstrated its direct and explicit concern to make the federal courts available to protect civil rights against unconstitutional actions of state courts.
  We summarized our conclusion in these words:
  “This legislative history makes evident that Congress clearly conceived that it was altering the relationship between the States and the Nation with respect to the protection of federally created rights; it was concerned that state instrumentalities could not protect those rights; it realized that state officers might, in fact, be antipathetic to the vindication of those rights; and it believed that these failings extended to the state courts.” 407 U. S., at 242.
  Thus, in Mitchum, absence of express language authorization for enjoining state-court proceedings in § 1983 actions was cured by the presence of relevant legislative history. In this case, however, neither the respondents nor the courts below have called to our attention any similar legislative history in connection with the enactment of § 16 of the Clayton Act. It is not suggested that Congress was concerned with the possibility that state-court proceedings would be used to violate the Sherman or Clayton Acts. Indeed, it seems safe to say that of the many and varied anticompeti-tive schemes which § 16 was intended to combat, Congress in no way focused upon a scheme using litigation in the state courts. The relevant legislative history of § 16 simply suggests that in enacting § 16 Congress was interested in extending the right to enjoin antitrust violations to private citizens. The critical aspects of the legislative history recounted in Mitchum which led us to conclude that § 1983 was within the “expressly authorized” exception to § 2283 are wholly absent from the relevant history of § 16 of the Clayton Act. This void is not filled by other evidence of congressional authorization.
  Section 16 undoubtedly embodies congressional policy favoring private enforcement of the antitrust laws, and undoubtedly there exists a strong national interest in antitrust enforcement. However, contrary to certain language in the opinion of the District Court, 403 F. Supp., at 536, the importance of the federal policy to be “protected” by the injunction is not the focus of the inquiry. Presumptively, all federal policies enacted into law by Congress are important, and there will undoubtedly arise particular situations in which a particular policy would be fostered by the granting of an injunction against a pending state-court action. If we were to accept respondents’ contention that § 16 could be given its “intended scope” only by allowing such injunctions, then § 2283 would be completely eviscerated since the ultimate logic of this position can mean no less than that virtually all federal statutes authorizing injunctive relief are exceptions to § 2283. Certainly all federal injunctive statutes are enacted to provide for the suspension of activities antithetical to the federal policies underlying the injunctive statute or related statutes. If the injunction would issue under the general rules of equity practice — requiring, inter alia, a showing of irreparable injury — but for the bar of § 2283, then clearly § 2283 in some sense may be viewed as frustrating or restricting federal policy since the activity inconsistent with the federal policy may not be enjoined because of § 2283’s bar. Thus, were we to accede to respondent’s interpretation of the “intended scope” language, an exception to § 2283 would always be found to be “necessary” to give the injunctive Act its full intended scope, and § 2283 would place no additional limitation on the right to enjoin state proceedings. The Anti-Injunction Act, a fixture in federal law since 1793, would then be a virtual dead letter whenever the plaintiff seeks an injunction under a federal injunctive statute. Whether or not the state proceeding could be enjoined would rest solely upon the traditional principles of equity and comity. However, as we emphasized in Mitchum, 407 U. S., at 243, the prohibitions of § 2283 exist separate and apart from these traditional principles, and we cannot read the “intended scope” language as rendering this specific and longstanding statutory provision inoperative simply because important federal policies are fostered by the statute under which the injunction is sought. Congress itself has found that these policies, in the ordinary case, must give way to the policies underlying § 2283. Given the clear prohibition of § 2283, the courts will not sit to balance and weigh the importance of various federal policies in seeking to determine which are sufficiently important to override historical concepts of federalism underlying § 2283; by the statutory scheme it has enacted, Congress has clearly reserved this judgment unto itself.
  Our conclusion that the “importance,” or the potential restriction in scope, of the federal injunction statute does not control for § 2283 purposes is consistent with the analysis of those veryjesotatutes which we have in..the.past held to be exceptions to the Anti-Injunction Act. See Mitchum, supra, at 234-235, and nn. 12-16. The original version of the Anti-Injunction Act itself was amended in 1874 to allow federal courts to enjoin state-court proceedings which interfere with the administration of a federal bankruptcy proceeding. Rev. Stat. § 720. The Interpleader Act of , 1926, 28 U. S. C, § 2361, the Frazier-Lemke Act, 11 U. S. C. § 203 (1940 ed.), and the Federal Habeas Corpus Act, 28 U. S. C. § 2251, while not directly referring to § 2283, have nonetheless explicitly, authorized injunctive relief against state-court proceedings. The Act of 1851 limiting liability of shipowners/ 46 U. S. C. § 185, provided that, after deposit of certain funds in the court by the shipowner, “all claims and proceedings against the owner with respect to the matter in question shall cease.” The statutory procedures for removal of a case from state court to federal court provide that the removal acts as a stay of the state-court proceedings. 28 U. S. C. § 1446 (e).
  By limiting the statutory exceptions of § 2283 and its predecessors to these few instances, we have clearly recognized that the Act countenancing the federal injunction must necessarily interact with, or focus upon, a state judicial proceeding. Section 16 of the Clayton Act, which does not by its very>s essence contemplate or envision any necessary interaction with) state judicial proceedings, is clearly not such an Act.
  IV
  Although the Court of Appeals did not reach the issue, the District Court found that, in addition to being “expressly authorized,” the injunction was “necessary in aid of its jurisdiction,” a separate exception to § 2283. The rationale of the District Court was as follows:
  “The Court also holds that § 2283 authorizes an injunction here because further collection efforts would eliminate two plaintiffs, Stoner Investments and Lektro-Vend Corp., as parties under the case or controversy provisions of Article III since they would necessarily be controlled by Vendo. Vendo’s offer to place the Stoner Investment and Lektro-Vend stock under control of the Court does not meet this problem because as a matter of substance Vendo would control both plaintiff and defendant, requiring dismissal under Article III. Thus the injunction is also necessary to protect the jurisdiction of the Court.” 403 F. Supp., at 536-537.
  In Toucey v. New York Life Ins. Co., 314 U. S., at 134-135, we acknowledged the existence of a historical exception to the Anti-Injunction Act in cases where the federal court has obtained jurisdiction over the res, prior to the state-court action. Although the “necessary in aid of” exception to § 2283 may be fairly read as incorporating this historical in rem exception, see C. Wright, Federal Courts § 47, p. 204 (3d ed. 1976), the federal and state actions here are simply in per- sonam. The traditional notion is that in personam actions in federal and state court may proceed concurrently, without interference from either court, and there is no evidence that the exception to § 2283 was intended to alter this balance. We have never viewed parallel in personam actions as interfering with the jurisdiction of either court; as we stated in Kline v. Burke Construction Co., 260 U. S. 226 (1922):
  “[A]n action brought to enforce [a personal liability] does not tend to impair or defeat the jurisdiction of the court in which a prior action for the same cause is pending. Each court is free to proceed in its own way and in its own time, without reference to the proceedings in the other court. Whenever a judgment is rendered in one of the courts and pleaded in the other, the effect of that judgment is to be determined by the application of the principles of res adjudicata . . . .” Id., at 230 (emphasis added).
  No case of this Court has ever held that an injunction to “preserve” a case or controversy fits within the “necessary in aid of its jurisdiction” exception; neither have the parties directed us to any other federal-court decisions so holding.
  The District Court’s legal conclusion is not only unsupported by precedent, but the factual premises upon which it rests are not persuasive. First, even if the two corporate plaintiffs would cease to litigate the case after execution of the state-court judgment, there is no indication that Harry Stoner himself would lose his standing to vindicate his rights, or that the case could not go forward. Nor does it appear that the two corporate plaintiffs would necessarily be removed from the lawsuit. As far as the record indicates, there are currently minority shareholders in those corporations whose ownership interests would not be affected by petitioner’s acquisition of majority stock control of the corporations. Under the applicable rules for shareholder derivative actions, see Fed. Rule Civ. Proc. 23.1, the shareholders could presumably pursue the corporate rights of action, which would inure to their benefit, even if the corporations themselves chose not to do so. Finally, petitioner offered to enter a consent decree which assuredly would eliminate any possibility of petitioner’s acquiring control of the corporations. See App. 209-210, 258. The injunction in this case was therefore, even under the District Courts’ legal theory, not necessary in aid of that court’s jurisdiction.
  Our conclusion that neither of the bases relied upon by the District Court constitutes an exception to § 2283 is more than consistent with the recognition that any doubt must be resolved against the finding of an exception to § 2283, Atlantic Coast Line R. Co., 398 U. S., at 297; a holding that there is an exception present in this case would demonstrably involve “judicial improvisation.” Clothing Workers, 348 U. S., at 514.
  Reversed and remanded.
  In addition to respondents Stoner and Stoner Manufacturing, petitioner also sued respondent Lektro-Vend Corp. Lektro-Vend had developed a radically new vending machine, and it was Stoner’s relationship with Lektro-Vend that formed the basis of the lawsuit.
  The Court of Appeals’ summary of the state-court litigation is illustrative:
  “The suit was filed in Kane County, Illinois on August 10, 1965; the complaint charged breach of noncompetition covenants; an amended complaint also charged theft of trade secrets. After a bench trial the court on December 16, 1966 found for Vendo. Judgments against Stoner for $250,000 and against both defendants for $1,100,000 were granted. Stoner and Stoner Investments were enjoined from further acts of competition.
  “An appeal was taken to the Appellate Court of Illinois. That court entered its decision on, January 30, 1969, . . . 105 Ill. App. 2d 261, 245 N. E. 2d 263. The court held that no trade secrets were involved, the noncompetition covenants were valid and enforceable, and the covenants had been breached by the defendants. The grant of injunctive relief was affirmed. The court also held that though the trial court erred in striking the affirmative defense based on the federal antitrust laws, it was correct in denying the defense based on the Illinois antitrust laws. The cause was remanded for a determination of damages and further proceedings.
  “Upon remand the defendant withdrew its affirmative defense asserted under the federal antitrust laws. The trial court, after hearing evidence, entered judgments against Stoner and Stoner Investments which totaled $7,363,500.
  “Upon a second appeal to the Illinois Appellate Court, the court decided, on September 12, 1973, 13 Ill. App. 3d 291, 300 N. E. 2d 632, that the trial court erred in the measurement of damages. The case was remanded for assessment of damages in accordance with the Appellate Court’s original opinion.
  "Upon appeal to the Illinois Supreme Court on September 27, 1974, . . . 58 Ill. 2d 289, 321 N. E. 2d 1, the appellate court was reversed and the trial court’s judgments were affirmed. The Supreme Court in deciding the case constructed a different theory of recovery — the breach of a fiduciary obligation on the part of Stoner — than had been asserted by Vendo.” 545 F. 2d 1050, 1055 n. 4 (CA7 1976).
  “Quite apart from any liability which may be predicated upon a breach of the covenants against competition contained in the sales agreement and the employment contract, it is clear that Stoner violated his fiduciary duties to plaintiff during the period when he was a director and an officer of plaintiff.” 58 Ill. 2d, at 303, 321 N. E. 2d, at 9.
  This issue was not presented to this Court in the petition for cer-tiorari, and the Court of Appeals did not discuss it in its opinion.
  Prior to the enactment of § 16, private injunctive relief was not authorized for antitrust violations. Paine Lumber Co. v. Neal, 244 U. S. 459 (1917). As far as the legislative history indicates, the sole purpose of § 16 (§ 14 in the original drafts) was to extend to private parties the right to sue for injunctive relief. The following passage, taken in its entirety from H. R. Rep. No. 627, 63d Cong., 2d Sess., 21 (1914), demonstrates what Congress had in mind in enacting § 16:
  “Section 14 authorizes a person, firm, or corporation or association to sue for and have injunctive relief against threatened loss or damage by a violation of the antitrust laws, when and under the same conditions and principles as injunctive relief against threatened conduct that will cause loss or damage is granted by courts of equity under the rules governing such proceedings. Under section 7 of the act of July 2, 1890, a person injured in his business and property by corporations or combinations acting in violation of the Sherman antitrust law, may recover loss and damage for such wrongful act. There is, however, no provision in the existing law authorizing a person, firm, corporation, or association to enjoin threatened loss or damage to his business or property by the commission of such unlawful acts, and the purpose of this section is to remedy such defect in the law. This provision is in keeping with the recommendation made by the President in his message to Congress on the subject of trusts and monopolies.”
  See also S. Rep. No. 698, 63d Cong., 2d Sess., 17-18 (1914).
  In California Motor Transport Co. v. Trucking Unlimited, 404 U. S. 508 (1972), this Court held that harassing and sham state-court proceedings of a repetitive nature could be part of an anticompetitive scheme or conspiracy. In Otter Tail Power Co. v. United States, 410 U. S. 366 (1973), one of the allegations was that the federal-court defendant had instituted and supported state-court litigation for anticompetitive purposes in violation of the antitrust laws. The District Court had enjoined the defendant from “[instituting, supporting or engaging in litigation, directly or indirectly, against cities and towns, and officials thereof, which have voted to establish municipal power systems . . . .” Jurisdictional Statement, O. T. 1972, No. 71-991, p. A-115. This Court vacated and remanded to the District Court for consideration, in light of the intervening decision of California Motor Transport, of whether the state-court litigation came within the “mere sham” exception announced in Eastern Railroad Presidents Conference v. Noerr Motor Freight, Inc., 365 U. S. 127 (1961). Those cases together may be cited for the proposition that repetitive, sham litigation in state courts may constitute an antitrust violation and that an injunction may he to enjoin future state-court litigation. However, neither of those cases involved the injunction of a pending state-court proceeding, and thus the bar of § 2283 was not brought into play.
  Nothing that we say today cuts back in any way on the holdings of these two cases; what we must here decide is whether such a lawsuit may be enjoined by a federal court after it has been commenced, notwithstanding the bar of the Anti-Injunction Act. While we conclude that it may not, nothing in our opinion today prevents a federal court in the proper exercise of its jurisdiction from enjoining the commencement of additional state-court proceedings if it concludes from the course and outcome of the first one that such proceedings would constitute a violation of the antitrust laws. With respect to this future litigation, the injunction will prevent even the commencement of a second such action, and the principles of federalism do not require the bar of § 2283. This distinction' is totally consistent with the realization that the true bona fides of the initial state-court litigation is often not apparent :
  “One claim, which a court or agency may think baseless, may go unnoticed; but a pattern of baseless, repetitive claims may emerge which leads the factfinder to conclude that the administrative and judicial processes have been abused.” California Motor Transport, supra, at 513.
  Any “disadvantage” to which the federal plaintiff is put in the initial proceeding is diminished by his ability to set up the federal antitrust claim as an affirmative defense, reviewable by this Court under 28 U. S. C. § 1257 (3), and his ability to sue for treble damages resulting from the vexatious prosecution of that state-court litigation.
  Petitioner has catalogued the following federal statutes, and suggests that each would be so^ affected:
  “E. g., 7 U. S. C. § 216 (§ 315 of the Packers and Stockyards Act of 1921); 7 U. S. C. §2050a (Farm Labor Contractor Registration Act); 7 U. S. C. § 2305 (a) (§ 6 of the Agricultural Fair Practices Act of 1967) ; 12 U. S. C. § 1731b (i) (§ 513 of the National Housing Act); 12 U. S. C. § 1976 (Bank Holding Company Act); 15 U. S. C. § 78aa (Securities Exchange Act of 1934); 15 U. S. C. § 298 (relating to the false stamping of gold and silver); 15 U. S. C. § 433 (providing for suits by farmer’s cooperative associations against discrimination by boards of trade); 15 U. S. C. §§ 1114 (2), 1116, 1121 (providing for injunctive relief against trademark infringement); 15 U. S. C. § 2073 (Consumer Product Safety Act); 15 U. S. C. § 2102 (Hobby Protection Act); 17 U. S. C. § 112 (providing for injunctions against violation of any right sechred by the copyright laws); 26 U. S. C. § 9011 (b) (Presidential Election Campaign Fund Act); 29 U. S. C. § 412 (Labor-Management Reporting and Discl&sure Act); 42 U. S. C. §2000e-5 (Title VII (Equal Employment Opportunities) of the Civil Rights Act of 1964); 42 U. S. C. §§ 6305, 6395 (e) (Energy Policy and Conservation Act); 45 U. S. C. § 547 (Title III of the Rail Passenger Service Act of 1970); 49 U. S. C. §§ 1 (20), 322 (b)(2), 916, 1017(b) (Interstate Commerce Act); 49 U. S. C. § 1487 (a) (Federal Aviation Act). See also 16 II. S. C. § 1540 (g) (Endangered Species Act of 1973); 33 U. S. C. § 1365 (Federal Water Pollution Control Act); 33 IT. S. C. § 1415 (g) (Marine Protection, Research, and Sanctuaries Act of 1972); 33 U. S. C. § 1515 (Deepwater Ports Act of 1974); 42 IT. S. C. § 300j-8 (Safe Drinking Water Act); 42 IT. S. C. § 1857h-2 (Clean Air Act); 42 IT. S. C. § 4911 (Noise Control Act of 1972).” Reply Brief for Petitioner 10-11, n. 7.
  Mr. Justice SteveNs in his dissent, see post, at 649-654, would conclude that since certain types of state-court litigation may violate the antitrust laws, an injunction of such litigation while pending is “expressly authorized” under the provisions of the Anti-Injunction Act. But this conclusion does not at all follow from the premise that judicial decisions have construed the prohibition of the antitrust laws to include sham and frivolous state-court proceedings — a premise with which we do not at all disagree, see n. 6, supra. The conclusion is supportable only as a matter of policy preference, and not of statutory construction. Under Mr. Justice SteveNs’ view, all a federal court need do is find a violation of the federal statute, then by the very force of that finding “express authorization” for the statute would be presumed. But this approach flies in the face of our past decisions. For example, in Mitchum v. Foster, 407 U. S. 225, 227 (1972), the petitioner had alleged that the state courts “were depriving him of rights protected by the First and Fourteenth Amendments.” Under Mr. Justice Stevens’ syllogistic formulation, since the state-court action is a violation of § 1983, the express authorization would be readily found on the face of the statute. However, the Court in Mitchum found no such ipso facto shortcut to the explicit prohibition of § 2283, but resorted to careful analysis of the legislative history in order to find evidence of congressional authorization. In short, Mr. Justice Stevens’ approach, which removes the bar of § 2283 from all federal injunctive statutes, is totally inconsistent with this Court’s longstanding recognition that “[legislative policy is here expressed in a clear-cut prohibition qualified only by specifically defined exceptions.” Clothing Workers v. Richman Bros. Co., 348 U. S. 511, 516 (1955).
  In reaching this conclusion, Mr. Justice Stevens argues that the Anti-Injunction Act should be “considered wholly inapplicable to later enacted federal statutes that are enforceable exclusively in federal litigation.” Post, at 659. But this view is inconsistent with the approach adopted by the Court in Clothing Workers, supra. In that case, an employer had sought an injunction against a union in state court. This Court found that the action before the state court was “outside state authority,” 348 U. S., at 514, and that jurisdiction was vested solely in the National Labor Relations Board. But the Court found that the exclusive federal jurisdiction was not sufficient to render §2283 inapplicable. See also Atlantic Coast Line R. Co. v. Locomotive Engineers, 398 U. S. 281 (1970).
  We think Mr. Justice Stevens’ view tends to confuse the jurisdiction granted to federal courts by § 16 of the Clayton Act with the separate question of whether a court having such jurisdiction has also been “expressly authorize^]” to enjoin state-court proceedings. Post, at 650-654. But the question of whether an injunction against state-court proceedings has been “expressly authorized” under § 2283 never arises unless the federal court asked to issue the injunction has subject-matter jurisdiction of the case in which the injunction is sought. Here the District Court is entirely free to proceed with the litigation on the merits of respondents’ antitrust claim against petitioner, and to grant damages and such other relief as may be appropriate if it determines the issues in favor of respondents. All that we conclude is that it may not include as a part of that relief an injunction against an already pending state-court proceeding.
  Much of Mr. Justice SteveNs’ dissenting opinion is an able brief for the conceded importance of the Sherman and Clayton Acts. But however persuasive it might be in inducing Congress to lift the bar of § 2283 with respect to injunctions issued under § 16, we do not believe it is persuasive in determining whether, under the present state of the law, Congress has in fact “expressly authorized1’ the injunction issued by the District Court here. For example, Mr. Justice SteveNs laments that state-court proceedings may now become the vehicles by which an antitrust violator may put one independent businessman after another out of business. See post, at 652-654, 657. Federal courts are -able to enjoin future repetitive litigation, see discussion of California Motor Transport and Otter Tail Power, supra, n. 6. But even if one were to agree with this broad speculation, the solution is simple and straightforward. If Congress determines that the use of state-court proceedings to foster anticompeti-tive schemes is of sufficient gravity, it may simply conclude that the need for greater antitrust enforcement outweighs the need to prevent friction in our federal system and amend § 16 to expressly authorize an injunction of state-court proceedings.
  No desire for more vigorous antitrust enforcement should cause us to lose sight of our role as judges in interpreting the explicit command of a congressional statute; for notwithstanding the rhetoric of the dissenting opinion, the conclusion that §16 is an “expressly authorized” exception to § 2283 is no more than an ipse dixit. The “explicit wording of § 2283,” Atlantic Coast Line R. Co., supra, at 297, is lost on the dissent; the dissent’s approach is the clearest form of judicial improvisation which the Court counseled against in Clothing Workers v. Richman Bros. Co., supra, at 514.
  A possible exception is Porter v. Dicken, 328 U. S. 252 (1946), regarding § 205 (a) of the Emergency Price Control Act of 1942. This Act, enacted in response to wartime exigencies, expired in 1947.