[16]*16Mb. Justice Douglas
delivered the opinion of the Court.
Petitioners are members of a Mormon sect, known as Fundamentalists. They not only believe in polygamy; unlike other Mormons,1 they practice it. Each of petitioners, except Stubbs, has, in addition to his lawful wife, one or more plural wives. Each transported at least one plural wife across state lines,2 either for the purpose of cohabiting with her, or for the purpose of aiding another member of the cult in such a project. They were convicted of violating the Mann Act (36 Stat. 825, 18 U. S. C. § 398) on a trial to the court, a jury having been waived. 56 F. Supp. 890. The judgments of conviction were affirmed on appeal. 146 F. 2d 730. The cases are here on petitions for certiorari which we granted in view of the asserted conflict between the decision below and Mortensen v. United States, 322 U. S. 369.
The Act makes an offense the transportation in interstate commerce of “any woman or girl for the purpose of prostitution or debauchery, or for any other immoral purpose.” The decision turns on the meaning of the latter phrase, “for any other immoral purpose.”
United States v. Bitty, 208 U. S. 393, involved a prosecution under a federal statute making it a crime to import an alien woman “for the purpose of prostitution or for any other immoral purpose.” The act was construed to cover a case where a man imported an alien woman so that she should live with him as his concubine. Two years later the Mann Act was passed. Because of the similarity of the language used in the two acts, the Bitty case became [17]*17a forceful precedent for the construction of the Mann Act. Thus one who transported a woman in interstate commerce so that she should become his mistress or concubine was held to have transported her for an “immoral purpose” within the meaning of the Mann Act. Caminetti v. United States, 242 U. S. 470.
It is argued that the Caminetti decision gave too wide a sweep to the Act; that the Act was designed to cover only the white slave business and related vices; that it was not designed to cover voluntary actions bereft of sex commercialism; and that in any event it should not be construed to embrace polygamy which is a form of marriage and, unlike prostitution or debauchery or the concubinage involved in the Caminetti case, has as its object parenthood and the creation and maintenance of family life. In support of that interpretation an exhaustive legislative history is submitted which, it is said, gives no indication that the Act was aimed at polygamous practices.
While Mortensen v. United States, supra, p. 377, rightly indicated that the Act was aimed “primarily” at the use of interstate commerce for the conduct of the white slave business, we find no indication that a profit motive is a sine qua non to its application. Prostitution, to be sure, normally suggests sexual relations for hire.3 But debauchery has no such implied limitation. In common understanding the indulgence which that term suggests may be motivated solely by lust.4 And so we start with words which [18]*18by their natural import embrace more than commercialized sex. What follows is “any other immoral purpose.” Under the ejusdem generis rule of construction the general words are confined to the class and may not be used to enlarge it. But we could not give the words a faithful interpretation if we confined them more narrowly than the class of which they are a part.
That was the view taken by the Court in the Bitty and Caminetti cases. We do not stop to reexamine the Cam-inetti case to determine whether the Act was properly applied to the facts there presented. But we adhere to its holding, which has been in force for almost thirty years,5 that the Act, while primarily aimed at the use of interstate commerce for the purposes of commercialized sex, is not restricted to that end.
We conclude, moreover, that polygamous practices are not excluded from the Act. They have long been outlawed in our society. As stated in Reynolds v. United States, 98 U.S. 145, 164:
“Polygamy has always been odious among the northern and western nations of Europe, and, until the establishment of the Mormon Church, was almost exclusively a feature of the life of Asiatic and of African people. At common law, the second marriage was always void (2 Kent, Com. 79), and from the earliest history of England polygamy has been treated as an offence against society.”
[19]*19As subsequently stated in Mormon Church v. United States, 136 U. S. 1, 49, “The organization of a community for the spread and practice of polygamy is, in a measure, a return to barbarism. It is contrary to the spirit of Christianity and of the civilization which Christianity has produced in the Western world.” And see Davis v. Beason, 133 U. S. 333. Polygamy is a practice with far more pervasive influences in society than the casual, isolated transgressions involved in the-Caminetti case. The establishment or maintenance of polygamous households is a notorious example of promiscuity. The permanent advertisement of their existence is an example of the sharp repercussions which they have in the community. We could conclude that Congress excluded these practices from the Act only if it were clear that the Act is confined to commercialized sexual vice. Since we cannot say it is, we see no way by which the present transgressions can be excluded. These polygamous practices have long been branded as immoral in the law. Though they have different ramifications, they are in the same genus as the other immoral practices covered by the Act.
The fact that the regulation of marriage is a state matter does not, of course, make the Mann Act an unconstitutional interference by Congress with the police powers of the States. The power of Congress over the instrumen-talities of interstate commerce is plenary; it may be used to defeat what are deemed to be immoral practices; and the fact that the means used may have “the quality of police regulations” is not consequential. Hoke v. United States, 227 U. S. 308, 323; see Athanasaw v. United States, 227 U. S. 326; Wilson v. United States, 232 U. S. 563.
Petitioners' second line of defense is that the requisite purpose was lacking.
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[16]*16Mb. Justice Douglas
delivered the opinion of the Court.
Petitioners are members of a Mormon sect, known as Fundamentalists. They not only believe in polygamy; unlike other Mormons,1 they practice it. Each of petitioners, except Stubbs, has, in addition to his lawful wife, one or more plural wives. Each transported at least one plural wife across state lines,2 either for the purpose of cohabiting with her, or for the purpose of aiding another member of the cult in such a project. They were convicted of violating the Mann Act (36 Stat. 825, 18 U. S. C. § 398) on a trial to the court, a jury having been waived. 56 F. Supp. 890. The judgments of conviction were affirmed on appeal. 146 F. 2d 730. The cases are here on petitions for certiorari which we granted in view of the asserted conflict between the decision below and Mortensen v. United States, 322 U. S. 369.
The Act makes an offense the transportation in interstate commerce of “any woman or girl for the purpose of prostitution or debauchery, or for any other immoral purpose.” The decision turns on the meaning of the latter phrase, “for any other immoral purpose.”
United States v. Bitty, 208 U. S. 393, involved a prosecution under a federal statute making it a crime to import an alien woman “for the purpose of prostitution or for any other immoral purpose.” The act was construed to cover a case where a man imported an alien woman so that she should live with him as his concubine. Two years later the Mann Act was passed. Because of the similarity of the language used in the two acts, the Bitty case became [17]*17a forceful precedent for the construction of the Mann Act. Thus one who transported a woman in interstate commerce so that she should become his mistress or concubine was held to have transported her for an “immoral purpose” within the meaning of the Mann Act. Caminetti v. United States, 242 U. S. 470.
It is argued that the Caminetti decision gave too wide a sweep to the Act; that the Act was designed to cover only the white slave business and related vices; that it was not designed to cover voluntary actions bereft of sex commercialism; and that in any event it should not be construed to embrace polygamy which is a form of marriage and, unlike prostitution or debauchery or the concubinage involved in the Caminetti case, has as its object parenthood and the creation and maintenance of family life. In support of that interpretation an exhaustive legislative history is submitted which, it is said, gives no indication that the Act was aimed at polygamous practices.
While Mortensen v. United States, supra, p. 377, rightly indicated that the Act was aimed “primarily” at the use of interstate commerce for the conduct of the white slave business, we find no indication that a profit motive is a sine qua non to its application. Prostitution, to be sure, normally suggests sexual relations for hire.3 But debauchery has no such implied limitation. In common understanding the indulgence which that term suggests may be motivated solely by lust.4 And so we start with words which [18]*18by their natural import embrace more than commercialized sex. What follows is “any other immoral purpose.” Under the ejusdem generis rule of construction the general words are confined to the class and may not be used to enlarge it. But we could not give the words a faithful interpretation if we confined them more narrowly than the class of which they are a part.
That was the view taken by the Court in the Bitty and Caminetti cases. We do not stop to reexamine the Cam-inetti case to determine whether the Act was properly applied to the facts there presented. But we adhere to its holding, which has been in force for almost thirty years,5 that the Act, while primarily aimed at the use of interstate commerce for the purposes of commercialized sex, is not restricted to that end.
We conclude, moreover, that polygamous practices are not excluded from the Act. They have long been outlawed in our society. As stated in Reynolds v. United States, 98 U.S. 145, 164:
“Polygamy has always been odious among the northern and western nations of Europe, and, until the establishment of the Mormon Church, was almost exclusively a feature of the life of Asiatic and of African people. At common law, the second marriage was always void (2 Kent, Com. 79), and from the earliest history of England polygamy has been treated as an offence against society.”
[19]*19As subsequently stated in Mormon Church v. United States, 136 U. S. 1, 49, “The organization of a community for the spread and practice of polygamy is, in a measure, a return to barbarism. It is contrary to the spirit of Christianity and of the civilization which Christianity has produced in the Western world.” And see Davis v. Beason, 133 U. S. 333. Polygamy is a practice with far more pervasive influences in society than the casual, isolated transgressions involved in the-Caminetti case. The establishment or maintenance of polygamous households is a notorious example of promiscuity. The permanent advertisement of their existence is an example of the sharp repercussions which they have in the community. We could conclude that Congress excluded these practices from the Act only if it were clear that the Act is confined to commercialized sexual vice. Since we cannot say it is, we see no way by which the present transgressions can be excluded. These polygamous practices have long been branded as immoral in the law. Though they have different ramifications, they are in the same genus as the other immoral practices covered by the Act.
The fact that the regulation of marriage is a state matter does not, of course, make the Mann Act an unconstitutional interference by Congress with the police powers of the States. The power of Congress over the instrumen-talities of interstate commerce is plenary; it may be used to defeat what are deemed to be immoral practices; and the fact that the means used may have “the quality of police regulations” is not consequential. Hoke v. United States, 227 U. S. 308, 323; see Athanasaw v. United States, 227 U. S. 326; Wilson v. United States, 232 U. S. 563.
Petitioners' second line of defense is that the requisite purpose was lacking. It is said that those petitioners who already had plural wives did not transport them in interstate commerce for an immoral purpose. The test laid [20]*20down in the Mortensen case was whether the transportation was in fact “the use of interstate commerce as a calculated means for effectuating sexual immorality.” 322 U. S. p. 375. There was evidence that this group of petitioners in order to cohabit with their plural wives found it necessary or convenient to transport them in interstate commerce and that the unlawful purpose was the dominant motive. In one case the woman was transported for the purpose of entering into a plural marriage. After a night with this petitioner she refused to continue the plural marriage relationship. But guilt under the Mann Act turns on the purpose which motivates the transportation, not on its accomplishment. Wilson v. United States, supra, pp. 570-71.
It is also urged that the requisite criminal intent was lacking since petitioners were motivated by a religious belief. That defense claims too much. If upheld, it would place beyond the law any act done under claim of religious sanction. But it has long been held that the fact that polygamy is supported by a religious creed affords no defense in a prosecution for bigamy. Reynolds v. United States, supra. Whether an act is immoral within the meaning of the statute is not to be determined by the accused’s concepts of morality. Congress has provided the standard. The offense is complete if the accused intended to perform, and did in fact perform, the act which the statute condemns, viz., the transportation of a woman for the purpose of making her his plural wife or cohabiting with her as such.
We have considered the remaining objections raised and find them without merit.
Affirmed.
Mr. Justice Black and Mr. Justice Jackson think that the cases should be reversed. They are of opinion that affirmance requires extension of the rule announced [21]*21in the Caminetti case and that the correctness of that rule is so dubious that it should at least be restricted to its particular facts.