them alone, though perfectly law-abiding, to indiscriminate and repeated interception and interrogation by public officials-thus bears an inseparable relationship to the welfare and tranquillity of all the states, and not merely to the welfare and tranquillity of one. Laws imposing such burdens are not mere census requirements, and even though they may be immediately associated with the accomplishment of a local purpose, they provoke questions in the field of international affairs. And specialized regulation of the conduct of an alien before naturalization is a matter which Congress must consider in discharging its constitutional duty "To establish an Uniform Rule of Naturalization . . ." It cannot be doubted that both the state and the federal registration laws belong "to that class of laws which concern the exterior relation of this whole nation with other nations and governments.' "10 Consequently the regulation of aliens is so intimately blended and intertwined with responsibilities of the national government that where it acts, and the state also acts on the same subject, "the act of Congress, or the treaty, is supreme; and the law of the State, though enacted in the exercise of powers not controverted, must yield to it." 17 And where the federal government, in the exercise of its superior authority in this field, has enacted a complete scheme of regulation and has therein provided a standard for the registration of aliens, states cannot, inconsistently with the purpose of Congress, conflict or interfere with, curtail or complement, the federal law, or enforce additional or aux

17

Henderson v. Mayor of New York, 92 U. S. 259, 273.

Gibbons v. Ogden, 9 Wheat. 1, 211; see Charleston & Western Carolina Ry. Co. v. Varnville Furniture Co., 237 U. S. 597. Cf. People v. Compagnie Générale Transatlantique, 107 U. S. 59, 63, where the Court, speaking of a state law and a federal law dealing with the same type of control over aliens, said that the federal law "covers the same ground as the New York statute, and they cannot co-exist."

52

Opinion of the Court.

iliary regulations.18 There is not-and from the very nature of the problem there cannot be any rigid formula or rule which can be used as a universal pattern to determine the meaning and purpose of every act of Congress. This Court, in considering the validity of state laws in the light of treaties or federal laws touching the same subject, has made use of the following expressions: conflicting; contrary to; occupying the field; repugnance; difference; irreconcilability; inconsistency; violation; curtailment; and interference.19 But none of these expressions provides an infallible constitutional test or an exclusive constitutional yardstick. In the final analysis, there can be no one crystal clear distinctly marked formula. Our primary function is to determine whether, under the circumstances of this particular case, Pennsylvania's law stands as an obstacle to the accomplishment and execution of the full purposes and objectives of Congress.20 And in

18 Cf. Nielsen v. Johnson, 279 U. S. 47; Asakura v. Seattle, 265 U. S. 332; International Shoe Co. v. Pinkus, 278 U. S. 261, 265, and cases there cited. And see Savage v. Jones, 225 U. S. 501, 539. Appellant relies on Gilbert v. Minnesota, 254 U. S. 325, and Halter v. Nebraska, 205 U. S. 34, but neither of those cases is relevant to the issues here presented.

19 E. g., Hauenstein v. Lynham, 100 U. S. 483, 489; Geofroy v. Riggs, 133 U. S. 258, 267; Asakura v. Seattle, 265 U. S. 332, 340, 342; Nielsen v. Johnson, 279 U. S. 47, 52; Todok v. Union State Bank, 281 U. S. 449, 454; Santovincenzo v. Egan, 284 U. S. 30, 40; United States v. Belmont, 301 U. S. 324, 331 (but compare the affirmance by an equally divided Court in United States v. Moscow Fire Ins. Co., 309 U. S. 624); Kelly v. Washington, 302 U. S. 1, 10, 11; Maurer v. Hamilton, 309 U. S. 598, 604; Bacardi Corporation v. Domenech, 311 U. S. 150, 157, 167..

20 Cf. Savage v. Jones, 225 U. S. 501, 533: "For when the question is whether a Federal act overrides a state law, the entire scheme of the statute must of course be considered and that which needs must be implied is of no less force than that which is expressed. If the purpose of the act cannot otherwise be accomplished-if its operation within its chosen field else must be frustrated and its provisions be refused their natural effect-the state law must yield to the regulation of Congress within the sphere of its delegated power."

that determination, it is of importance that this legislation is in a field which affects international relations, the one aspect of our government that from the first has been most generally conceded imperatively to demand broad national authority. Any concurrent state power that may exist is restricted to the narrowest of limits; the state's power here is not bottomed on the same broad base as is its power to tax. And it is also of importance that this legislation deals with the rights, liberties, and personal freedoms of human beings, and is in an entirely different category from state tax statutes or state pure food laws regulating the labels on cans.2

21

22

Our conclusion is that appellee is correct in his contention that the power to restrict, limit, regulate, and register aliens as a distinct group is not an equal and continuously existing concurrent power of state and nation, but that whatever power a state may have is subordinate to supreme national law.23 We proceed there

21

'Express recognition of the breadth of the concurrent taxing powers of state and nation is found in Federalist paper No. 32.

"It is true that where the Constitution does not of itself prohibit state action, as in matters related to interstate commerce, and where the Congress, while regulating related matters, has purposely left untouched a distinctive part of a subject which is peculiarly adapted to local regulation, the state may legislate concerning such local matters which Congress could have covered but did not. Kelly v. Washington, 302 U. S. 1, 9, 10, 11, 12, 13, 14 (inspection for seaworthiness of hull and machinery of motor-driven tugs). And see Reid v. Colorado, 187 U. S. 137, 147 (prohibition on introduction of diseased cattle or horses); Savage v. Jones, 225 U. S. 501, 529, 532 (requirement that certain labels reveal package contents); Carey v. South Dakota, 250 U. S. 118, 121 (prohibition of shipment by carrier of wild ducks); Dickson v. Uhlmann Grain Co., 288 U. S. 188, 199 (prohibition of margin transactions in grain where there is no intent to deliver); Mintz v. Baldwin, 289 U. S. 346, 350-352 (inspection of cattle for infectious diseases); Maurer v. Hamilton, 309 U. S. 598, 604, 614 (prohibition of car-over-cab trucking).

"As supporting the contention that the state can enforce its alien registration legislation, even though Congress has acted on the identical

fore to an examination of Congressional enactments to ascertain whether or not Congress has acted in such manner that its action should preclude enforcement of Pennsylvania's law.

Second. For many years Congress has provided a broad and comprehensive plan describing the terms and conditions upon which aliens may enter this country, how they may acquire citizenship, and the manner in which they may be deported. Numerous treaties, in return for reciprocal promises from other governments, have pledged the solemn obligation of this nation to the end that aliens residing in our territory shall not be singled out for the imposition of discriminatory burdens. Our Constitution and our Civil Rights Act have guaranteed to aliens "the equal protection of the laws [which] is a pledge of the protection of equal laws." 24 With a view to limiting prospective residents from foreign lands to those possessing the qualities deemed essential to good and useful citizenship in America, carefully defined qualifications are required to be met before aliens may enter our country. These qualifications include rigid requirements as to health, education, integrity, character, and adaptability to our institutions. Nor is the alien left free from the

subject, appellant relies upon a number of previous opinions of this Court. Ohio ex rel. Clarke v. Deckebach, 274 U. S. 392, 395, 396; Frick v. Webb, 263 U. S. 326, 333; Webb v. O'Brien, 263 U. S. 313, 321, 322; Terrace v. Thompson, 263 U. S. 197, 223, 224; Heim v. McCall, 239 U. S. 175, 193, 194. In each of those cases this Court sustained state legislation which applied to aliens only, against an attack on the ground that the laws violated the equal protection clause of the Constitution. In each case, however, the Court was careful to point out that the state law was not in violation of any valid treaties adopted by the United States, and in no instance did it appear that Congress had passed legislation on the subject. In the only case of this type in which there was an outstanding treaty provision in conflict with the state law, this Court held the state law invalid. Asakura v. Seattle, 265 U. S. 332.

"Yick Wo v. Hopkins, 118 U. S. 356, 369.

application of federal laws after entry and before naturalization. If during the time he is residing here he should be found guilty of conduct contrary to the rules and regulations laid down by Congress, he can be deported. At the time he enters the country, at the time he applies for permission to acquire the full status of citizenship, and during the intervening years, he can be subjected to searching investigations as to conduct and suitability for citizenship.25 And in 1940 Congress added to this comprehensive scheme a complete system for alien registration.

26

The nature of the power exerted by Congress, the object sought to be attained, and the character of the obligations imposed by the law, are all important in considering the question of whether supreme federal enactments preclude enforcement of state laws on the same subject. Opposition to laws permitting invasion of the personal liberties of law-abiding individuals, or singling out aliens as particularly dangerous and undesirable groups, is deep-seated in this country. Hostility to such legislation in America stems back to our colonial history," and champions of freedom for the individual have always vigorously opposed burdensome registration systems. The drastic requirements of the alien Acts of 1798 28 brought about a political upheaval in this country the repercussions from which have not even yet wholly subsided.29 So violent was the reaction to the 1798 laws that almost a century elapsed before a second registration

258 U. S. C. §§ 152, 373, 377 (c), 382, 398, 399 (a). "Cf. Prigg v. Pennsylvania, 16 Pet. 539, 622, 623.

27

"As early as 1641, in the Massachusetts "Body of Liberties," we find the statement that "Every person within this Jurisdiction, whether inhabitant or forreiner, shall enjoy the same justice and law that is generall for the plantation . . .”

28 1 Stat. 570, 577.

"See Field, J., dissenting in Fong Yue Ting v. United States, 149 U. S. 698, 746-750. Cf. 84 Cong. Rec. 9534.