Mr. Justice DOUGLAS delivered the opinion of the Court.

[Appeal from an order of the United States District Court for the Central District of California, granting motion to dismiss indictment charging appellees with possession of unregistered hand grenades in violation of 26 U.S.C. § 5861(d), on the ground that the indictment did] not allege the element of scienter.  The case is here on direct appeal. . . .

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II

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[p. 607]

 The Act requires no specific intent or knowledge that the hand grenades were unregistered.  It makes it unlawful for any person 'to receive or possess a firearm which is not registered to him.' [n. 12] By the lower court decisions at the time that requirement was witten into the Act the only knowledge required to be proved was knowledge that the instrument possessed was a firearm.  See Sipes v. United States, 8 Cir., 321 F.2d 174, 179, and cases cited.

12. 26 U.S.C., s 5861(d) (1964 ed., Supp. V).

'(W)here Congress borrows terms of art in which are accumulated the legal tradition and meaning [p. 608] of centuries of practice, it presumably knows and adopts the cluster of ideas that were attached to each borrowed word in the body of learning from which it was taken and the meaning its use will convey to the judicial mind unless otherwise instructed.' Id., at 263, 72 S.Ct., at 250.

 At the other extreme is Lambert v. California, 355 U.S. 225, 78 S.Ct. 240, 2 L.Ed.2d 228, in which a municipal code made it a crime to remain in Los Angeles for more than five days without registering if a person had been convicted of a felony.  Being in Los Angeles is not per se blameworthy.  The mere failure to register, we held, was quite 'unlike the commission of acts, or the failure to act under circumstances that should alert the doer to the consequences of his deed.' Id., at 228, 78 S.Ct., at 243.  The fact that the ordinance was a convenient law enforcement technique did not save it.

'Where a person did not know of the duty to register and where there was no proof of the probability of such knowledge, he may not be convicted consistently with due process.  Were it otherwise, the evil would be as great as it is when the law is written in print too fine to read or in a language foreign to the community.' Id., at 229--230, 78 S.Ct., at 243--244.

 [p. 609] In United States v. Dotterweich, 320 U.S. 277, 284, 64 S.Ct. 134, 138, 88 L.Ed. 48, a case dealing with the imposition of a penalty on a corporate officer whose firm shipped adulterated and misbranded drugs in violation of the Food and Drug Act, we approved the penalty 'though consciousness of wrong-doing be totally wanting.'

 The present case is in the category neither of Lambert nor Morissette, but is closer to Dotterweich. This is a regulatory measure in the interest of the public safety, which may well be premised on the theory that one would hardly be surprised to learn that possession of hand grenades is not an innocent act. [n. 14] They are highly dangerous offensive weapons, no less dangerous than the narcotics involved in United States v. Balint, 258 U.S. 250, 254, 42 S.Ct. 301, 303, 66 L.Ed. 604, where a defendant was convicted of sale of narcotics against his claim that he did not know the drugs were covered by a federal act.  We say with Chief Justice Taft in that case:

14. We need not decide whether a criminal conspiracy to do an act 'innocent in itself' and not known by the alleged conspirators to be prohibited must be actuated by some corrupt motive other than the intention to do the act which is prohibited and which is the object of the conspiracy.  An agreement to acquire hand grenades is hardly an agreement innocent in itself.  Therefore what we have said of the substantive offense satisfies on these special facts the requirements for a conspiracy.  Cf. United States v. Mack, 2 Cir., 112 F.2d 290.

 Reversed.
 

 MR. JUSTICE BRENNAN, concurring in the judgment of reversal.

 . . . . I do not join Part II of the opinion; although I reach the same result as the Court on the intent the Government must prove to convict, I do so by another route.

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 The Court's discussion of the intent the Government must prove to convict appellees of violation of 26 U.S.C. s 5861(d) (1964 ed. Supp. V) does not dispel the confusion surrounding a difficult, but vitally important, area of the law.  This case does not raise questions of 'consciousness of wrongdoing' or 'blameworthiness.'  If the ancient maxim that 'ignorance of the law is no excuse' has any residual validity, it indicates that the ordinary intent requirement--mens rea--of the criminal law does not require knowledge that an act is illegal, wrong, or blameworthy.  Nor is it possible to decide this case by a simple process of classifying the statute involved as a 'regulatory' or a 'public welfare' measure.  To convict appellees of possession of unregistered hand grenades, the Government must prove three material elements: (1) that appellees possessed certain items; (2) that the items possessed were hand grenades; and (3) that the hand grenades were not registered.  The Government and the Court agree that the prosecutor must prove knowing possession of the items and also knowledge that the items possessed were hand grenades.  Thus, while the Court does hold that no intent at all need be proved in regard to one element of the offense--the unregistered status of the grenades--knowledge must still be proved as to the other two elements. Consequently, the National Firearms Act does not create a crime of strict liability as to all its elements.  It is no help in deciding what level of intent must be proved as [p. 613] to the third element to declare that the offense falls within the 'regulatory' category.

 Following the analysis of the Model Penal Code, [n. 3] I think we must recognize, first, that '(t)he existence of a mens rea is the rule of, rather than the exception to, the principles of Anglo-American criminal jurisprudence.'  Dennis v. United States, 341 U.S. 494, 500, 71 S.Ct. 857, 862, 95 L.Ed. 1137 (1951) (Vinson, C.J., announcing judgment); Smith v. California, 361 U.S. 147, 150, 80 S.Ct. 215, 217, 4 L.Ed.2d 205 (1959); [n. 4] second, that mens rea is not a unitary concept, but may vary as to each element of a crime; and third, that Anglo-American law has developed several identifiable and analytically distinct levels of intent, e.g., negligence, recklessness, knowledge, and purpose. [n. 5]  To determine the mental element required for conviction, each material element of the offense must be examined and the determination made what [p. 614] level of intent Congress intended the Government to prove, taking into account constitutional considerations, see Screws v. United States, 325 U.S. 91, 65 S.Ct. 1031, 89 L.Ed. 1495 (1945), as well as the common-law background, if any, of the crime involved.  See  Morissette v. United States, 342 U.S. 246, 72 S.Ct. 240, 96 L.Ed. 288 (1952).

3. ALI Model Penal Code s 2.02, Comment 123--132 (Tent.  Draft No. 4, 1955).
 
4. 'Still, it is doubtless competent for the (government) to create strict criminal liabilities by defining criminal offenses without any element of scienter--though * * * there is precedent in this Court that this power is not without limitations.  See Lambert v. California, 355 U.S. 225, 78 S.Ct. 240, 2 L.Ed.2d 228.'  Smith v. California, 361 U.S. 147, 150, 80 S.Ct. 215, 217, 4 L.Ed.2d 205 (1959).  The situations in which strict liability may be imposed were stated by Judge, now Mr. Justice, Blackmun: '(W)here a federal criminal statute omits mention of intent and where it seems to involve what is basically a matter of policy, where the standard imposed is, under the circumstances, reasonable and adherence thereto properly expected of a person, where the penalty is relatively small, where conviction does not gravely besmirch, where the statutory crime is not one taken over from the common law, and where congressional purpose is supporting, the statute can be construed as one not requiring criminal intent.'  Holdridge v. United States, 282 F.2d 302, 310 (CA8 1960).

5. These different levels of intent are defined in the code.  ALI Model Penal Code s 2.02 (Prop.Official Draft 1962).  This Court has relied on the code's definitions.  Leary v. United States, 395 U.S. 6, 46 n. 93, 89 S.Ct. 1532, 1553, 23 L.Ed.2d 57 (1969); Turner v. United States, 396 U.S. 398, 416 n. 29, 90 S.Ct. 642, 652, 24 L.Ed.2d 610 (1970).

 The third element--the unregistered status of the grenades--presents more difficulty.  Proof of intent with regard to this element would require the Government to show that the appellees knew that the grenades were [p. 615] unregistered or negligently or recklessly failed to ascertain whether the weapons were registered. It is true that such a requirement would involve knowledge of law, but it does not involve 'consciousness of wrongdoing' in the sense of knowledge that one's actions were prohibited or illegal. [n. 6] Rather, the definition of the crime, as written by Congress, requires proof of circumstances that involve a legal element, namely whether the grenades were registered in accordance with federal law.  The knowledge involved is solely knowledge of the circumstances that the law has defined as material to the offense.  The Model Penal Code illustrates the distinction:

6. Proof of some crimes may include a requirement of proof of actual knowledge that the act was prohibited by law, or proof of a purpose to bring about the forbidden result.  See James v. United States, 366 U.S. 213, 81 S.Ct. 1052, 6 L.Ed.2d 246 (1961); Boyce Motor Lines v. United States, 342 U.S. 337, 72 S.Ct. 329, 96 L.Ed. 367 (1952).  United States v. Murdock, 290 U.S. 389, 54 S.Ct. 223, 78 L.Ed. 381 (1933).  See generally Note. Counseling Draft Resistance: The Case for a Good Faith Belief Defense, 78 Yale L.J. 1008, 1022--1037 (1969).  Cf. Model Penal Code s 2.02(2)(a) (Prop.Official Draft 1962) (definition of 'purposely').

 Therefore, as with the first two elements, the question is solely one of congressional intent.  And while the question is not an easy one, two factors persuade me that proof of mens rea as to the unregistered status of the grenades is not required.  First, as the Court notes, the case law under the provisions replaced by the current law dispensed with proof of intent in connection with this element.  Sipes v. United States, supra. Second, the firearms covered by the Act are major weapons such as machineguns and sawed-off shotguns; deceptive weapons such as flashlight guns and fountain pen guns; and major destructive devices such as bombs, grenades, mines, rockets, and large caliber weapons including mortars, anti-tank guns, and bazookas.  Without exception, the likelihood of governmental regulation of the distribution of such weapons is so great that anyone must be presumed to be aware of it.  In the context of a taxing and registration scheme, I therefore think it reasonable to conclude that Congress dispensed with the requirement of intent in regard to the unregistered status of the weapon, as necessary to effective administration of the statute.