Justice O’Connor
delivered the opinion of the Court.
This case concerns the scope of two criminal statutes enacted by Congress to enforce the Thirteenth Amendment. Title 18 U. S. C. §241 prohibits conspiracy to interfere with an individual’s Thirteenth Amendment right to be free from “involuntary servitude.” Title 18 U. S. C. § 1584 makes it a crime knowingly and willfully to hold another person “to involuntary servitude.” We must determine the meaning of “involuntary servitude” under these two statutes.
I
In 1983, two mentally retarded men were found laboring on a Chelsea, Michigan, dairy farm in poor health, in squalid conditions, and in relative isolation from the rest of society. The operators of the farm — Ike Kozminski, his wife Marga-rethe, and their son John — were charged with violating 18 U. S. C. §241 by conspiring to “injure, oppress, threaten, or intimidate” the two men in the free exercise and enjoyment of their federal right to be free from involuntary servitude. The Kozminskis were also charged with knowingly holding, or aiding and abetting in the holding of, the two men to involuntary servitude in violation of 18 U. S. C. §1584 and §2 The case was tried before a jury in the United States District Court for the Eastern District of Michigan. The Government’s evidence is summarized below.
The victims, Robert Fulmer and Louis Molitoris, have intelligence quotients of 67 and 60 respectively. ' Though chronologically in their 60’s during the period in question, they viewed the world and responded to authority as would someone of 8 to 10 years. Margarethe Kozminski picked Fulmer up one evening in 1967 while he was walking down the road, and brought him to work at one of the Kozminski farms. He was working on another farm at the time, but Mrs. Kozminski simply left a note telling his former employer that he had gone. Molitoris was living on the streets of Ann Arbor, Michigan, in the early 1970’s when Ike Kozminski brought him to work on the Chelsea farm. He had previously spent several years at a state mental hospital.
Fulmer and Molitoris worked on the Kozminskis’ dairy farm seven days a week, often 17 hours a day, at first for $15 per week and eventually for no pay. The Kozminskis subjected the .two men to physical and verbal abuse for failing to do their work and instructed herdsmen employed at the farm to do The same. The Kozminskis directed Fulmer and Molitoris not to leave the farm, and on several occasions when the men did leave,' the Kozminskis or their employees brought the men back and discouraged them from leaving again. On one occasion, John Kozminski threatened Molitoris with institutionalization if he did not do as he was told.
The Kozminskis failed to provide Fulmer and Molitoris with adequate nutrition, housing, clothing, or medical care. They directed the two men not to talk to others and discouraged the men from contacting their relatives. At the same time, the Kozminskis discouraged relatives, neighbors, farm hands, and visitors from contacting Fulmer and Molitoris. Fulmer and Molitoris asked others for help in leaving the farm, and eventually a herdsman hired by the Kozminskis was concerned about the two men and notified county officials! of their condition. County officials assisted Fulmer and Molitoris in leaving the farm and placed them in an adult foster care home.
In attempting to persuade the jury that the Kozminskis held their victims in involuntary servitude, the Government did not rely solely on evidence regarding their use or threatened use of physical force or the threat of institutionalization. Rather, the Government argued that the Kozminskis had used various coercive measures — including denial of pay, subjection to substandard living conditions, and isolation from others — to cause the victims to believe they had no alternative but to work on the farm. The Government argued that Fulmer and Molitoris were “psychological hostages” whom the Kozminskis had “brainwash[ed]” into serving them. Tr. 15, 23.
At the conclusion of the evidence, the District Court instructed the jurors that in order to convict the Kozminskis of conspiracy under §241, they must find (1) the existence of a conspiracy including the Kozminskis, (2) that the purpose of the conspiracy was to injure, oppress, threaten, or intimidate a United States citizen in the free exercise or enjoyment of a federal right to be free from involuntary servitude, and (3) that one of the conspirators knowingly committed an overt act in furtherance of that purpose. The court further instructed the jury that §1584 required the Government to prove' (1) that the Kozminskis held the victims in involuntary servitude, (2) that they acted knowingly or willfully, and (3) that their actions were a necessary cause of the victims’ decision to continue working for them. The court delivered the following instruction on the meaning of involuntary servitude under both statutes:
“Involuntary servitude consists of two terms.
“Involuntary means ‘done contrary to or without choice’ — ‘compulsory’ — ‘not subject to control of the will.’
“Servitude means ‘[a] condition in which a person lacks liberty especially to determine one’s course of action or ■way of life’ — ‘slavery’ — ‘the state of being subject to a master.’
“Involuntary servitude involves a condition of having some of the incidents of slavery.
“It may include situations in which persons are forced to return to employment by law.
“It may also include persons who are physically restrained by guards from leaving employment.
“It may also include situations involving either physical and other coercion, or a combination thereof, used to ■detain persons in employment.
' “In other words, based on all the evidence it will be for ;you to determine if there was a means of compulsion .used, sufficient in kind and degree, to subject a person having the same general station in life as the alleged victims to believe they had no reasonable means of escape and no choice except to remain in the service of the employer.” App. to Pet. for Cert. 109a-110a.
So instructed, the jury found Ike and Margarethe Kozmin-ski guilty of violating both statutes. John Kozminski was convicted only on the § 241 charge. Each of the Kozminskis was placed on probation for two years. In addition, Ike Koz-minski was fined $20,000 and was ordered to pay $6,190.80 in restitution to each of the victims. John Kozminski was fined $10,000.
.A divided panel of the Court of Appeals for the Sixth Circuit affirmed the convictions. App.- to Pet. for Cert. 72a. After rehearing the case en banc, however, the Court of Appeals reversed the convictions and remanded the case for a new trial. 821 F. 2d 1186 (1987). The majority concluded that the District Court’s definition of involuntary servitude, which would bring cases involving general psychological coercion within the reach of § 241 and § 1584, was too broad. The court held that involuntary servitude exists only when •
“(a) the servant believes that he or she has no viable alternative but to perform service for the master (b) because of (1) the master’s use or threatened use of physical force, or (2) the master’s use or threatened use of state-imposed legal coercion (i. e., peonage), or (3) the master’s use of fraud or deceit to obtain or maintain services where the servant is a minor, an immigrant or one who is mentally incompetent.” 821 F. 2d, at 1192 (footnote omitted).
The dissenting judges charged that the majority had “rewritten rather than interpreted” § 1584. Id., at 1213. They argued that involuntary servitude may arise from whatever means the defendant intentionally uses to subjugate the will of the victim so as to render the victim “ ‘incapable of making a rational choice.’” Id., at 1212-1213 (quoting United States v. Shackney, 333 F. 2d 475, 488 (CA2 1964) (Dimock, J., concurring)).
The Court of Appeals’ definition of involuntary servitude conflicts with the definitions adopted by other Courts of Appeals. Writing for the Second Circuit in United States v. Shackney, supra, Judge Friendly reasoned that
“a holding in involuntary servitude means to us action by the master causing the servant to have, or to believe he has, no way to avoid continued service or confinement, . . . not a situation where the servant knows he has a choice between continued service and freedom, even if the master has led him to believe that the choice may entail consequences that are exceedingly bad.” Id., at 486.
Accordingly, Judge Friendly concluded that § 1584 prohibits only “service compelled by law, by force or by the threat of continued confinement of some sort.” Id., at 487. See also United States v. Harris, 701 F. 2d 1095, 1100 (CA4 1983) (involuntary servitude exists under § 241 and § 1584 where labor is coerced by “threat of violence or confinement, backed sufficiently by deeds”); United States v. Bibbs, 564 F. 2d 1165, 1168 (CA5 1977) (involuntary servitude exists under § 1584 where the defendant places the victim “in such fear of physical harm that the victim is afraid to leave”). The Ninth Circuit, in contrast, has not limited the reach of § 1584 to cases involving physical force or legal sanction, but has concluded that
“[a] holding in involuntary servitude occurs when an individual coerces another into his service by improper or wrongful conduct that is intended to cause, and does cause, the other person to believe that he or she has no alternative but to perform labor.” United States v. Mussry, 726 F. 2d 1448, 1453 (1984).
See also United States v. Warren, 772 F. 2d 827, 833-834 (CA11 1985) (“Various forms of coercion may constitute a holding in involuntary servitude. The use, or threatened use, of physical force to create a climate of fear is the most grotesque example of such coercion”).
We granted the Government’s petition for a writ of certio-rari, 484 U. S. 894 (1987), to resolve this conflict among the Courts of Appeals on the meaning of involuntary servitude for the purpose of criminal prosecution under §241 and § 1584.'
II
Federal crimes are defined by Congress, and so long as Congress acts within its constitutional power in enacting a criminal statute, this Court must give effect to Congress’ expressed intention concerning the scope of conduct prohibited. See Dowling v. United States, 473 U. S. 207, 213, 214 (1985) (citing United States v. Wiltberger, 5 Wheat. 76, 95 (1820)). Congress’ power to enforce the Thirteenth Amendment by enacting § 241 and § 1584 is clear and undisputed. See U. S. Const., Arndt. 13, §2 (“Congress shall have power to enforce this article by appropriate legislation”); Griffin v. Breckenridge, 403 U. S. 88, 105 (1971). The scope of conduct prohibited by these statutes is therefore a matter of statutory construction.
The Court of Appeals reached its conclusions regarding the meaning of involuntary servitude under both § 241 and § 1584 based solely on its analysis of the language and history of § 1584. A reading of these statutes, however, reveals an obvious difference between them. Unlike § 1584, which by its terms prohibits holding to involuntary servitude, §241 prohibits conspiracies to interfere with rights secured “by the Constitution or laws of the United States,” and thus incorporates the prohibition of involuntary servitude contained in the Thirteenth Amendment. See United States v. Price, 383 U. S. 787, 805 (1966). The indictment in this casé, which was read to the jury, specifically charged the Kozminskis with conspiring to interfere with the “right and privilege secured ... by the Constitution and laws of the United States to be free from involuntary servitude as provided by the Thirteenth Amendment of the United States Constitution.” App. 177 (emphasis added). Thus, the indictment clearly specified a conspiracy to violate the Thirteenth Amendment. The indictment cannot be read to charge a conspiracy to violate § 1584 rather than the Thirteenth Amendment, because the criminal sanction imposed by § 1584 does not create any individual “right or privilege” as those words are used in §241. The Government has not conceded that the definition of involuntary servitude as used in the Thirteenth Amendment is limited by the meaning of the same phrase in § 1584. To the contrary, the Government argues (1) that the Thirteenth Amendment should be broadly construed, and (2) that Congress did not intend § 1584 to have a narrower scope. Brief for United States 22-32. The District Court defined involuntary servitude broadly under both § 241 and § 1584. The Court of Appeals reversed the convictions under both counts because it concluded that the definition of involuntary servitude given for each count was erroneous. Since the proper interpretation of each statute is squarely before us, we construe each statute separately to ascertain the conduct it prohibits.
A
Section 241 authorizes punishment when
“two or more persons conspire to injure, oppress, threaten, or intimidate any citizen in the free exercise or enjoyment of any right or privilege secured to him by the Constitution or laws of the United States, or because of his having so exercised the same.”
This Court interpreted the purpose and effect of § 241 over 20 years ago in United States v. Guest, 383 U. S. 745 (1966), and United States v. Price, supra. Section 241 creates no substantive rights, but prohibits interference with rights established by the Federal Constitution or laws and by decisions interpreting them. Guest, supra, at 754-755; Price, supra, at 803. Congress intended the statute to incorporate by reference a large body of potentially evolving federal law. This Court recognized, however, that a statute prescribing criminal punishment must be interpreted in a manner that provides a definite standard of guilt. The Court resolved the tension between these two propositions by construing §241 to prohibit only intentional interference with rights made specific either by the express terms of the Federal Constitution or laws or by decisions interpreting them. Price, supra, at 806, n. 20; Guest, supra, at 754-755. Cf. Screws v. United States, 325 U. S. 91, 102 (1945).
The Kozminskis were convicted under § 241 for conspiracy to interfere with the Thirteenth Amendment guarantee against involuntary servitude. Applying the analysis set out in Price and Guest, our task is to ascertain the precise definition of that crime by looking to the scope of the Thirteenth Amendment prohibition of involuntary servitude specified in our prior decisions.
The Thirteenth Amendment declares that “[njeither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction.” The Amendment is “self-executing without any ancillary legislation, so far as its terms are applicable to any existing state of circumstances,” Civil Rights Cases, 109 U. S. 3, 20 (1883), and thus establishes a constitutional guarantee that is protected by §241. See Price, supra, at 805. The primary purpose of the Amendment was to abolish the institution of African slavery as it had existed in the United States at the time of the Civil War, but the Amendment was not limited to that purpose; the phrase “involuntary servitude” was intended to extend “to cover those forms of compulsory labor akin to African slavery which in practical operation would tend to produce like undesirable results.” Butler v. Perry, 240 U. S. 328, 332 (1916). See also Robertson v. Baldwin, 165 U. S. 275, 282 (1897); Slaughter-House Cases, 16 Wall. 36, 69 (1873).
While the general spirit of the phrase “involuntary servitude” is easily comprehended, the exact range of conditions it prohibits is harder to define. The express exception of involuntary servitude imposed as a punishment for crime provides some guidance. The fact that the draf ters felt it necessary to exclude this situation indicates that they thought involuntary servitude includes at least situations in which the victim is compelled to work by law. Moreover, from the general intent to prohibit conditions “akin to African slavery,” see Butler v. Perry, supra, at 332-333, as well as the fact that the Thirteenth Amendment extends beyond state action, compare U. S. Const., Arndt. 14, §1, we readily can deduce an intent to prohibit compulsion through physical coercion.
This judgment is confirmed when we turn to our previous decisions construing the Thirteenth Amendment. Looking behind the broad statements of purpose to the actual holdings, we find that in every case in which this Court has found a condition of involuntary servitude, the victim had no available choice but to work or be subject to legal sanction. In Clyatt v. United States, 197 U. S. 207 (1905), for example, the Court recognized that peonage — a condition in which the victim is coerced by threat of legal sanction to work off a debt to a master — is involuntary servitude under the Thirteenth Amendment. Id., at 215, 218. Similarly, in United States v. Reynolds, 235 U. S. 133 (1914), the Court held that “[cjompulsion of. . . service by the constant fear of imprisonment under the criminal laws” violated “rights intended to be secured by the Thirteenth Amendment.” Id., at 146, 150. In that case the Court struck down a criminal surety system under which a person fined for a misdemeanor offense could contract to work for a surety who would, in turn, pay the convict’s fine to the State. The critical feature of the system was that that breach of the labor contract by the convict was a crime. The convict was thus forced to work by threat of criminal sanction. The Court has also invalidated state laws subjecting debtors to prosecution and criminal punishment for failing to perform labor after receiving an advance payment. Pollock v. Williams, 322 U. S. 4 (1944); Taylor v. Georgia, 315 U. S. 25 (1942); Bailey v. Alabama, 219 U. S. 219 (1911). The laws at issue in these cases made failure to perform services for which money had been obtained prima facie evidence of intent to defraud. The Court reasoned that “the State could not avail itself of the sanction of the criminal law to supply the compulsion [to enforce labor] any more than it could use or authorize the use of physical force.” Bailey, supra, at 244.
Our precedents reveal that not all situations in which labor is compelled by physical coercion or force of law violate the Thirteenth Amendment. By its terms the Amendment excludes involuntary servitude imposed as legal punishment for a crime. Similarly, the Court has recognized that the prohibition against involuntary servitude does not prevent the State or Federal Governments from compelling their citizens, by threat of criminal sanction, to perform certain civic duties. See Hurtado v. United States, 410 U. S. 578, 589, n. 11 (1973) (jury service); Selective Draft Law Cases, 245 U. S. 366, 390 (1918) (military service); Butler v. Perry, supra (roadwork). Moreover, in Robertson v. Baldwin, 165 U. S. 275 (1897), the Court observed that the Thirteenth Amendment was not intended to apply to “exceptional” cases well established in the common law at the time of the Thirteenth Amendment, such as “the right of parents and guardians to the custody of their minor children or wards,” id., at 282, or laws preventing sailors who contracted to work on vessels from deserting their ships. Id., at 288.
Putting aside such exceptional circumstances, none of which are present in this case, our precedents clearly define a Thirteenth Amendment prohibition of involuntary servitude enforced by the use or threatened use of physical or legal coercion. The guarantee of freedom from involuntary servitude has never been interpreted specifically to prohibit compulsion of labor by other means, such as psychological coercion. We draw no conclusions from this historical survey about the potential scope of the Thirteenth Amendment. Viewing the Amendment, however, through the narrow window that is appropriate in applying §241, it is clear that the Government cannot prove a conspiracy to violate rights secured by the Thirteenth Amendment without proving that the conspiracy involved the use or threatened use of physical or legal coercion.
B
Section 1584 authorizes criminal punishment of
“[w]hoever knowingly and willfully holds to involuntary servitude or sells into any condition of involuntary servitude any other person for any term.”
This is our first occasion to consider the reach of this statute. The pivotal phrase, “involuntary servitude,” clearly was borrowed from the Thirteenth Amendment. Congress’ use of the constitutional language in a statute enacted pursuant to its constitutional authority to enforce the Thirteenth Amendment guarantee makes the conclusion that Congress intended the phrase to have the same meaning in both places logical, if not inevitable. In the absence of any contrary indications, we therefore give effect to congressional intent by construing “involuntary servitude” in a way consistent with the understanding of the Thirteenth Amendment that prevailed at the time of § 1584’s enactment. See United States v. Shackney, 333 F. 2d 475 (CA2 1964) (Friendly, J.).
Section 1584 was enacted as part of the 1948 revision to the Criminal Code. At that time, all of the Court’s decisions identifying conditions of involuntary servitude had involved compulsion of services through the use or threatened use of physical or legal coercion. See, e. g., Clyatt v. United States, supra; United States v. Reynolds, supra; Pollock v. Williams, supra; Bailey v. Alabama, supra. By employing the constitutional language, Congress apparently was focusing on the prohibition of comparable conditions.
The legislative history of § 1584 confirms this conclusion and undercuts the Government’s claim that Congress had a broader concept of involuntary servitude in mind. No significant legislative history accompanies the 1948 enactment of § 1584; the statute was adopted as part of a general revision of the Criminal Code. The 1948 version of § 1584 was a consolidation, however, of two earlier statutes: the Slave Trade statute, as amended in 1909, formerly 18 U. S. C. §423 (1940 ed.), and the 1874 Padrone statute, formerly 18 U. S. C. §446 (1940 ed.). There are some indications that § 1584 was intended to have the same substantive reach as these statutes. See, e. g., A. Holtzoff, Preface to Title 18 •U. S. C. A. (1969) (“In general, with a few exceptions, the Code does not attempt to change existing law”); Revision of Titles 18 and 28 of the United States Code: Hearings on H. R. 1600 and H. R. 2055 before Subcommittee No. 1 of the House Committee on the Judiciary, 80th Cong., 1st Sess., 13-14 (1947) (statement of advisory committee member Justin Miller). But see United States v. Shackney, supra, at 482 (viewing changes made in the course of consolidation as significant and § 1584 as positive law). Whether or not § 1584 was intended to track these earlier statutes exactly, it was most assuredly not intended to work a radical change in the law. We therefore review the legislative history of the Slave Trade statute and the Padrone statute to inform our construction of § 1584.
The original Slave Trade statute authorized punishment of persons who “hold, sell, or otherwise dispose of any. . . negro, mulatto, or person of colour, so brought [into the United States] as a slave, or to be held to service or labour.” Act of Apr. 20, 1818, ch. 91, § 6, 3 Stat. 452. This statute was one of several measures passed in the early 19th century for the purpose of ending the African slave trade. A 1909 amendment removed the racial restriction, extending the statute to the holding of “any person” as a slave. This revision, however, left unchanged that portion of the statute describing the condition under which such persons were held. See 42 Cong. Rec. 1114 (1908). The Government attempts to draw a contrary conclusion from a comment by Senator Heyburn to the effect that the 1909 amendment was intended to protect vulnerable people who were brought into the United States for labor or for immoral purposes. Id., at 1115. This comment is inconclusive, however. Other Senators expressly disagreed with the view that the elimination of the racial restriction changed the meaning of the word “slavery.” See id., at 1114-1115. Moreover, the 1909 reenactment of the Slave Trade statute was part of a general codification of the federal penal laws, which Senator Heyburn himself stated was “in no instance to change the practice of the law.” Id., at 2226. Thus, we conclude that nothing in the history of the Slave Trade statute suggests that it was intended to extend to conditions of servitude beyond those applied to slaves, i. e., physical or legal coercion.
The other precursor of § 1584, the Padrone statute, reflects a similarly limited scope. The “padrones” were men who took young boys away from their families in Italy, brought them to large cities in the United States, and put them to work as street musicians or beggars. Congress enacted the Padrone statute in 1874 “to prevent [this] practice of enslaving, buying, selling, or using Italian children.” 2 Cong. Rec. 4443 (1874) (Rep. Cessna). The statute provided that
“whoever shall knowingly and wilfully bring into the United States . . . any person inveigled or forcibly kidnapped in any other country, with intent to hold such person ... in confinement or to any involuntary service, and whoever shall knowingly and wilfully sell, or cause to be sold, into any condition of involuntary servitude, any other person for any term whatever, and every person who shall knowingly and wilfully hold to involuntary service any person so sold and bought, shall be deemed guilty of a felony.” Act of June 23, 1874, ch. 464. 18 Stat. 251.
This statute, too, was aimed only at compulsion of service through physical or legal coercion. To be sure, use of the term “inveigled” indicated that the statute was intended to protect persons brought into this country by other means. But the statute drew a careful distinction between the manner in which persons were brought into the United States and the conditions in which they were subsequently held, which are expressly identified as “confinement” or “involuntary servitude.” Our conclusion that Congress believed these terms to be limited to situations involving physical or legal coercion is confirmed when we examine the actual physical conditions facing the victims of the padrone system. These young children were literally stranded in large, hostile cities in a foreign country. They were given no education or other assistance toward self-sufficiency. Without such assistance, without family, and without other sources of support, these children had no actual means of escaping the padrones’ service; they had no choice but to work for their masters or risk physical harm. The padrones took advantage of the special vulnerabilities of their victims, placing them in situations where they were physically unable to leave.
The history of the Padrone statute reflects Congress’ 'view that a victim’s age or special vulnerability may be relevant in determining whether a particular type or a certain degree of physical or legal coercion is sufficient to hold that person to involuntary servitude. For example, a child who is told he can go home late at night in the dark through a strange area may be subject to physical coercion that results in his staying, although a competent adult plainly would not be. Similarly, it is possible that threatening an incompetent with institutionalization or an immigrant with deportation could constitute the threat of legal coercion that induces involuntary servitude, even though such a threat made to an adult citizen of normal intelligence would be too implausible to produce involuntary servitude. But the Padrone statute does not support the Court of Appeals’ conclusion that involuntary servitude can exist absent the use or threatened use of physical or legal coercion to compel labor. Moreover, far from broadening the definition of involuntary servitude for immigrants, children, or mental incompetents, § 1584 eliminated any special distinction among, or protection of, special classes of victims.
Thus, the language and legislative history of § 1584 both indicate that its reach should be limited to cases involving the compulsion of services by the use or threatened use of physical or legal coercion. Congress chose to use the language of the Thirteenth Amendment in § 1584 and this was the scope of that constitutional provision at the time § 1584 was enacted.
c
The Government has argued that we should adopt a broad construction of “involuntary servitude,” which would prohibit the compulsion of services by any means that, from the victim’s point of view, either leaves the victim with no tolerable alternative but to serve the defendant or deprives the victim of the power of choice. Under this interpretation, involuntary servitude would include compulsion through psychological coercion as well as almost any other type of speech or conduct intentionally employed to persuade a reluctant person to work.
This interpretation would appear to criminalize a broad range of day-to-day activity. For example, the Government conceded at oral argument that, under its interpretation, §241 and § 1584 could be used .to punish a parent who coerced an adult son or daughter into working in the family business by threatening withdrawal of affection. Tr. of Oral Arg. 12. It has also been suggested that the Government’s construction would cover a political leader who uses charisma to induce others to work without pay or a religious leader who obtains personal services by means of religious indoctrination. See Brief in Opposition 4; Brief for the International Society for Krishna Consciousness of California, Inc., as Amicus Curiae 25. As these hypothetical suggest, the Government’s interpretation would delegate to prosecutors and juries the inherently legislative task of determining what type of coercive activities are so morally reprehensible that they should be punished as crimes. It would also subject individuals to the risk of arbitrary or discriminatory prosecution and conviction.
Moreover, as the Government would interpret the statutes, the type of coercion prohibited would depend entirely upon the victim’s state of mind. Under such a view, the statutes would provide almost no objective indication of the conduct or condition they prohibit, and thus would fail to provide fair notice to ordinary people who are required to conform their conduct to the law. The Government argues that any such difficulties are eliminated by a requirement that the defendant harbor a specific intent to hold the victim in involuntary servitude. But in light of the Government’s failure to give any objective content to its construction of the phrase “involuntary servitude,” this specific intent requirement amounts to little more than an assurance that the defendant sought to do “an unknowable something.” Screws v. United States, 325 U. S., at 105.
In short, we agree with Judge Friendly’s observation that
“[t]he most ardent believer in civil rights legislation might not think that cause would be advanced by permitting the awful machinery of the criminal law to be brought into play whenever an employee asserts that his will to quit has been subdued by a threat which seriously affects his future welfare but as to which he still has a choice, however painful.” United States v. Schackney, 333 F. 2d., at 487.
Accordingly, we conclude that Congress did not intend § 1584 to encompass the broad and undefined concept of involuntary servitude urged upon us by the Government.
Justice Brennan would hold that § 1584 prohibits not only the use or threatened use of physical or legal coercion, but also any means of coercion “that actually succeeds in reducing the victim to a condition of servitude resembling that in which slaves were held before the Civil War.” Post, at 962. This formulation would be useful if it were accompanied by a recognition that the use or threat of physical or legal coercion was a necessary incident of pre-Civil War slavery and thus of the “ ‘slavelike’ conditions of servitude Congress most clearly intended to eradicate.” Post, at 961. Instead, finding no objective factor to be necessary to a “slavelike condition,” Justice Brennan would delegate to prosecutors and juries the task of determining what working conditions are so oppressive as to amount to involuntary servitude.
Such a definition of involuntary servitude is theoretically -narrower than that advocated by the Government, but it suffers from the same flaws. The ambiguity in the phrase ' “slavelike conditions” is not merely a question of degree, but instead concerns the very nature of the conditions prohibited. Although we can be sure that Congress intended to prohibit ‘“slavelike’ conditions of servitude,” we have no indication that Congress thought that conditions maintained by means either than by the use or threatened use of physical or legal coercion were “slavelike.” Whether other conditions are so intolerable that they, too, should be deemed to be involuntary is a value judgment that we think is best left for Congress. ,
.Justice Stevens concludes that Congress intended to delegate to the Judiciary the inherently legislative task of defining “involuntary servitude” through case-by-case adjudication. Post, at 965. Neither the language nor the legislative history of § 1584 provides an adequate basis for such a conclusion. Reference to the Sherman Act does not advance Justice Stevens’ argument, for that Act does not authorize courts to develop standards for the imposition of criminal punishment. To the contrary, this Court determined that the objective standard to be used in deciding whether conduct violates the Sherman Act — the rule of reason — was evinced by the language and the legislative history of the Act. Standard Oil Co. v. United States, 221 U. S. 1, 60 (1911). It is one thing to recognize that some degree of uncertainty exists whenever judges and juries are called upon to apply substantive standards established by Congress; it would be quite another thing to tolerate the arbitrariness and unfairness of a legal system in which the judges would develop the standards for imposing criminal punishment on a case-by-case basis.
. Sound principles of statutory construction lead us to reject the amorphous definitions of involuntary servitude proposed by the Government and by Justices Brennan and Ste-VENS. By construing § 241 and § 1584 to prohibit only compulsion of services through physical or legal coercion, we adhere to the time-honored interpretive guideline that uncertainty concerning the ambit of criminal statutes should be resolved in favor of lenity. See, e. g., McNally v. United States, 483 U. S. 350 (1987); Dowling v. United States, 473 U. S. 207, 229 (1985); Liparota v. United States, 471 U. S. 419, 427 (1985); Rewis v. United States, 401 U. S. 808, 812 (1971). The purposes underlying the rule of lenity — to promote fair notice to those subject to the criminal laws, to minimize the risk of selective or arbitrary enforcement, and to maintain the proper balance between Congress, prosecutors, and courts — are certainly served by its application in this case.
. Ill
Absent change by Congress, we hold that, for purposes of criminal prosecution under § 241 or §1584, the term “involuntary servitude” necessarily means a condition of servitude in which the victim is forced to work for the defendant by the use or threat of physical restraint or physical injury, or by the use or threat of coercion through law or the legal process. This definition encompasses those cases in which the defendant holds the victim in servitude by placing the victim in fear of such physical restraint or injury or legal coercion. Our holding does not imply that evidence of other means of coercion, or of poor working conditions, or of the victim’s special vulnerabilities is irrelevant in a prosecution under these statutes. As we have indicated, the vulnerabilities of the victim are relevant in determining whether the physical or legal coercion or threats thereof could plausibly have compelled the victim to serve. In addition, a trial court could properly find that evidence of other means of coercion or of extremely poor working conditions is relevant to corroborate disputed evidence regarding the use or threatened use of physical or legal coercion, the defendant’s intention in using such means, or the causal effect of such conduct. We hold only that the jury must be instructed that compulsion of services by the use or threatened use of physical or legal coercion is a necessary incident of a condition of involuntary servitude.
The District Court’s instruction on involuntary servitude, which encompassed other means of coercion, may have caused the Kozminskis to be convicted for conduct that does not violate either statute. Accordingly, we agree with the Court of Appeals that the convictions must be reversed and the case remanded for a new trial.
We disagree with the Court of Appeals to the extent it determined that'a defendant could violate §241 or §1584 by means other than the use or threatened use of physical or legal coercion where the victim is a minor, an immigrant, or one who is mentally incompetent. But because we believe the record contains sufficient evidence of physical or legal coercion to enable a jury to convict the Kozminskis even under the stricter standard of involuntary servitude that we announce today, we agree with the Court of Appeals that a judgment of acquittal is unwarranted.
The judgment of the Court of Appeals is affirmed, and the case is remanded for further proceedings consistent with this opinion.
It is so ordered.
Title 18 U. S. C. § 2 provides, in pertinent part, that “[wjhoever commits an offense against the United States or aids, abets, counsels-, commands, induces or procures its commission, is punishable as a principal.”
The Government produced an expei-t witness who testified that the Kozminskis’ general treatment of the two men caused the men to undergo an “involuntary conversion” to complete dependency. App. to Pet. for Cert. 15a. The Court of Appeals held that this expert .testimony was admitted in violation of Federal Rule of Evidence 702. The Government has not sought review of this ruling, and we do not address it.