Mr. Justice Marshall
delivered the opinion of the Court.
In this case, petitioners challenge their convictions under the Travel Act, 18 U. S. C. § 1952, which prohibits interstate travel in furtherance of certain criminal activity. Although the United States Court of Appeals for the Fifth Circuit narrowed an expansive interpretation of the Act, the Court of Appeals affirmed petitioners’ convictions. For the reasons stated below, we reverse.
Petitioners, James Rewis and Mary Lee Williams, were convicted along with two other defendants in the United States District Court for the Middle District of Florida. Their convictions arose from a lottery, or numbers operation, which petitioners admittedly ran in Yulee, Florida, a small community located a few miles south of the Georgia-Florida state line. Petitioners are Florida residents, and there is no evidence that they at any time crossed state lines in connection with the operation of their lottery. The other two convicted defendants are Georgia residents who traveled from their Georgia homes to place bets at petitioners’ establishment in Yulee.
The District Court instructed the jury that mere bettors in a lottery violated Florida law, and that if the bettors traveled interstate for the purpose of gambling, they also violated the Travel Act. Presumably referring to petitioners, the District Court further charged that a defendant could be found guilty under the aiding and abetting statute, 18 U. S. C. § 2, without proof that he personally performed every act constituting the charged offense. On appeal, the Fifth Circuit held that § 1952 did not make it a federal crime merely to cross a state line for the purpose of placing a bet and reversed the convictions of the two Georgia residents because the evidence presented at trial was insufficient to show that they were anything other than customers of the gambling operation. However, the Court of Appeals upheld petitioners’ convictions on the ground that operators of gambling establishments are responsible for the interstate travel of their customers. 418 F. 2d 1218, 1222.
We agree with the Court of Appeals that it cannot be said, with certainty sufficient to justify a criminal conviction, that Congress intended that interstate travel by mere customers of a gambling establishment should violate the Travel Act. But we are unable to conclude that conducting a gambling operation frequented by out-of-state bettors, by itself, violates the Act. Section 1952 prohibits interstate travel with the intent to “promote, manage, establish, carry on, or facilitate” certain kinds of illegal activity; and the ordinary meaning of this language suggests that the traveler’s purpose must involve more than the desire to patronize the illegal activity. Legislative history of the Act is limited, but does reveal that § 1952 was aimed primarily at organized crime and, more specifically, at persons who reside in one State while operating or managing illegal activities located in another. In addition, we are struck by what Congress did not say. Given the ease with which citizens of our Nation are able to travel and the existence of many multi-state metropolitan areas, substantial amounts of criminal activity, traditionally subject to state regulation, are patronized by out-of-state customers. In such a context, Congress would certainly recognize that an expansive Travel Act would alter sensitive federal-state relationships, could overextend limited federal police resources, and might well produce situations in which the geographic origin of customers, a matter of happenstance, would transform relatively minor state offenses into federal felonies. It is not for us to weigh the merits of these factors, but the fact that they are not even discussed in the legislative history of § 1952 strongly suggests that Congress did not intend that the Travel Act should apply to criminal activity solely because that activity is at times patronized by persons from another State. In short, neither statutory language nor legislative history supports such a broad-ranging interpretation of § 1952. And even if this lack of support were less apparent, ambiguity concerning the ambit of criminal statutes should be resolved in favor of lenity, Bell v. United States, 349 U. S. 81, 83 (1955).
The Government concedes as much, but offers an alternative construction of the Travel Act — that the Act is violated whenever the operator of an illegal establishment can reasonably foresee that customers will cross state lines for the purpose of patronizing the illegal operation or whenever the operator actively seeks to attract business from another State. The first half of this proposed interpretation — reasonable foreseeability of interstate patronage — does not merit acceptance. Whenever individuals actually cross state fines for the purpose of patronizing a criminal establishment, it will almost always be reasonable to say that the operators of the establishment could have foreseen that some of their customers would come from out of State. So, for practical purposes, this alternative construction is almost as expansive as interpretations that we have already rejected. In addition, there is little, if any, evidence that Congress intended that foreseeability should govern criminal liability under § 1952.
There may, however, be greater support for the second half of the Government’s proposed interpretation — that active encouragement of interstate patronage violates the Act. Of course, the conduct deemed to constitute active encouragement must be more than merely conducting the illegal operation; otherwise, this interpretation would only restate other constructions which we have rejected. Still, there are cases in which federal courts have correctly applied § 1952 to those individuals whose agents or employees cross state fines in furtherance of illegal activity, see, e. g., United States v. Chambers, 382 F. 2d 910, 913-914 (CA6 1967); United States v. Barrow, 363 F. 2d 62, 64-65 (CA3 1966), cert. denied, 385 U. S. 1001 (1967); United States v. Zizzo, 338 F. 2d 577, 580 (CA7 1964), cert. denied, 381 U. S. 915 (1965), and the Government argues that the principles of those decisions should be extended to cover persons who actively seek interstate patronage. Although we are cited to no cases that have gone so far and although much of what we have said casts substantial doubt on the Government’s broad argument, there may be occasional situations in which the conduct encouraging interstate patronage so closely approximates the conduct of a principal in a criminal agency relationship that the Travel Act is violated. But we need not rule on this part of the Government’s theory because it is not the interpretation of § 1952 under which petitioners were convicted. The jury was not charged that it must find that petitioners actively sought interstate patronage. And we are not informed of any action by petitioners, other than actually conducting their lottery, that was designed to attract out-of-state customers. As a result, the Government’s proposed interpretation. of the Travel Act cannot be employed to uphold these convictions.
Reversed.
Mr. Justice White took no part in the decision of this case.
Title 18 U. S. C. § 1952 (1964 ed. and Supp. V) provides:
“(a) Whoever travels in interstate or foreign commerce or uses any facility in interstate or foreign commerce, including the mail, with intent to—
“(1) distribute the proceeds of any unlawful activity; or
“(2) commit any crime of violence to further any unlawful activity; or
“(3) otherwise promote, manage, establish, carry on, or facilitate the promotion, management, establishment, or carrying on, of any unlawful activity,
“and thereafter performs or attempts to perform any of the acts specified in subparagraphs (1), (2), and (3), shall be fined not more than $10,000 or imprisoned for not more than five years, or both.
“(b) As used in this section ‘unlawful activity’ means (1) any business enterprise involving gambling, liquor on which the Federal ■excise tax has not been paid, narcotics, or prostitution offenses in violation of the laws of the State in which they are committed or of the United States, or (2) extortion, bribery, or arson in violation of the laws of the State in which committed or of the United States.”
Petitioners were convicted of eight substantive -violations under § 1952 and of conspiracy to violate the section. Petitioner Rewis was sentenced to five years’ imprisonment on each count, to run concurrently. Petitioner Williams was sentenced to three years’ imprisonment on each count, to run concurrently, subject to parole under 18 U. S. C. §4208 (a) (2). Petitioner Rewis was also convicted of two counts of having failed to purchase a wagering tax stamp. These latter two convictions were reversed by the Court of Appeals under the intervening decisions of this Court in Marchetti v. United States, 390 U. S. 39 (1968), and Grosso v. United States, 390 U. S. 62 (1968).
18 U. S. C. § 2 provides:
“(a) Whoever commits an offense against the United States or aids, abets, counsels, commands, induces or procures its commission, is punishable as a principal.
“(b) Whoever willfully causes an act to be done which if directly performed by him or another would be an offense against the United States, is punishable as a principal.”
418 F. 2d 1218. The Government has not sought review of that part of the Court of Appeals decision reversing the conviction of the two Georgia residents.
Both parties correctly concede that the questions in this case are solely statutory. No issue of constitutional dimension is presented.
Incorporated in the Senate report (S. Rep. No. 644, 87th Cong., 1st Sess., 2-3, dated July 27, 1961) the following appears:
“The bill, S. 1653, was introduced by the chairman of the committee, Senator James O. Eastland, on April 18, 1961, on the recommendation of the Attorney General, Robert F. Kennedy, as a part of the Attorney General’s legislative program to combat organized crime and racketeering.
“The Attorney General testified before the committee in support of the bill, S. 1653, on June 6, 1961, and commented:
“ 'We are seeking to take effective action against the racketeer who conducts an unlawful business but lives far from the scene in comfort and safety, as well as against other hoodlums.
“ ‘Let me say from the outset that we do not seek or intend to impede the travel of anyone except persons engaged in illegal businesses as spelled out in the bill. . . .
“ ‘The target clearly is organized crime. The travel that would be banned is travel “in furtherance of a business enterprise” which involves gambling, liquor, narcotics, and prostitution offenses or extortion or bribery. Obviously, we are not trying to curtail the sporadic, casual involvement in these offenses, but rather a continuous course of conduct sufficient for it to be termed a business enterprise.’
“ ‘Our investigations also have made it quite clear that only the Federal Government can shut off the funds which permit the top men of organized crime to live far from the scene and, therefore, remain immune from the local officials.’ ”
attorney general of the United States, or his office specified state board or department of education city, town, township, village, or borough government or governmental unit state commission, board, committee, or authority county government or county governmental unit, except school district court or judicial district state department or agency governmental employee or job applicant female governmental employee or job applicant minority governmental employee or job applicant minority female governmental employee or job applicant not listed among agencies in the first Administrative Action variable retired or former governmental employee U.S. House of Representatives interstate compact judge state legislature, house, or committee local governmental unit other than a county, city, town, township, village, or borough governmental official, or an official of an agency established under an interstate compact state or U.S. supreme court local school district or board of education U.S. Senate U.S. senator foreign nation or instrumentality state or local governmental taxpayer, or executor of the estate of state college or university United States State person accused, indicted, or suspected of crime advertising business or agency agent, fiduciary, trustee, or executor airplane manufacturer, or manufacturer of parts of airplanes airline distributor, importer, or exporter of alcoholic beverages alien, person subject to a denaturalization proceeding, or one whose citizenship is revoked American Medical Association National Railroad Passenger Corp. amusement establishment, or recreational facility arrested person, or pretrial detainee attorney, or person acting as such;includes bar applicant or law student, or law firm or bar association author, copyright holder bank, savings and loan, credit union, investment company bankrupt person or business, or business in reorganization establishment serving liquor by the glass, or package liquor store water transportation, stevedore bookstore, newsstand, printer, bindery, purveyor or distributor of books or magazines brewery, distillery broker, stock exchange, investment or securities firm construction industry bus or motorized passenger transportation vehicle business, corporation buyer, purchaser cable TV car dealer person convicted of crime tangible property, other than real estate, including contraband chemical company child, children, including adopted or illegitimate religious organization, institution, or person private club or facility coal company or coal mine operator computer business or manufacturer, hardware or software consumer, consumer organization creditor, including institution appearing as such; e.g., a finance company person allegedly criminally insane or mentally incompetent to stand trial defendant debtor real estate developer disabled person or disability benefit claimant distributor person subject to selective service, including conscientious objector drug manufacturer druggist, pharmacist, pharmacy employee, or job applicant, including beneficiaries of employer-employee trust agreement, employee health and welfare fund, or multi-employer pension plan electric equipment manufacturer electric or hydroelectric power utility, power cooperative, or gas and electric company eleemosynary institution or person environmental organization employer. If employer's relations with employees are governed by the nature of the employer's business (e.g., railroad, boat), rather than labor law generally, the more specific designation is used in place of Employer. farmer, farm worker, or farm organization father female employee or job applicant female movie, play, pictorial representation, theatrical production, actor, or exhibitor or distributor of fisherman or fishing company food, meat packing, or processing company, stockyard foreign (non-American) nongovernmental entity franchiser franchisee lesbian, gay, bisexual, transexual person or organization person who guarantees another's obligations handicapped individual, or organization of devoted to health organization or person, nursing home, medical clinic or laboratory, chiropractor heir, or beneficiary, or person so claiming to be hospital, medical center husband, or ex-husband involuntarily committed mental patient Indian, including Indian tribe or nation insurance company, or surety inventor, patent assigner, trademark owner or holder investor injured person or legal entity, nonphysically and non-employment related juvenile government contractor holder of a license or permit, or applicant therefor magazine male medical or Medicaid claimant medical supply or manufacturing co. racial or ethnic minority employee or job applicant minority female employee or job applicant manufacturer management, executive officer, or director, of business entity military personnel, or dependent of, including reservist mining company or miner, excluding coal, oil, or pipeline company mother auto manufacturer newspaper, newsletter, journal of opinion, news service radio and television network, except cable tv nonprofit organization or business nonresident nuclear power plant or facility owner, landlord, or claimant to ownership, fee interest, or possession of land as well as chattels shareholders to whom a tender offer is made tender offer oil company, or natural gas producer elderly person, or organization dedicated to the elderly out of state noncriminal defendant political action committee parent or parents parking lot or service patient of a health professional telephone, telecommunications, or telegraph company physician, MD or DO, dentist, or medical society public interest organization physically injured person, including wrongful death, who is not an employee pipe line company package, luggage, container political candidate, activist, committee, party, party member, organization, or elected official indigent, needy, welfare recipient indigent defendant private person prisoner, inmate of penal institution professional organization, business, or person probationer, or parolee protester, demonstrator, picketer or pamphleteer (non-employment related), or non-indigent loiterer public utility publisher, publishing company radio station racial or ethnic minority person or organization protesting racial or ethnic segregation or discrimination racial or ethnic minority student or applicant for admission to an educational institution realtor journalist, columnist, member of the news media resident restaurant, food vendor retarded person, or mental incompetent retired or former employee railroad private school, college, or university seller or vendor shipper, including importer and exporter shopping center, mall spouse, or former spouse stockholder, shareholder, or bondholder retail business or outlet student, or applicant for admission to an educational institution taxpayer or executor of taxpayer's estate, federal only tenant or lessee theater, studio forest products, lumber, or logging company person traveling or wishing to travel abroad, or overseas travel agent trucking company, or motor carrier television station union member unemployed person or unemployment compensation applicant or claimant union, labor organization, or official of veteran voter, prospective voter, elector, or a nonelective official seeking reapportionment or redistricting of legislative districts (POL) wholesale trade wife, or ex-wife witness, or person under subpoena network slave slave-owner bank of the united states timber company u.s. job applicants or employees Army and Air Force Exchange Service Atomic Energy Commission Secretary or administrative unit or personnel of the U.S. Air Force Department or Secretary of Agriculture Alien Property Custodian Secretary or administrative unit or personnel of the U.S. Army Board of Immigration Appeals Bureau of Indian Affairs Bonneville Power Administration Benefits Review Board Civil Aeronautics Board Bureau of the Census Central Intelligence Agency Commodity Futures Trading Commission Department or Secretary of Commerce Comptroller of Currency Consumer Product Safety Commission Civil Rights Commission Civil Service Commission, U.S. Customs Service or Commissioner of Customs Defense Base Closure and REalignment Commission Drug Enforcement Agency Department or Secretary of Defense (and 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Reconstruction Finance Corp. Department or Secretary of Homeland Security Unidentifiable International Entity