Hire, Alaska Stat. Ann. § 38.40.090,5 included a one-year durational residency requirement. Appellants attacked that requirement as well as the flat employment preference given by Alaska Hire to state residents. By agreement of the parties, consideration of a motion for a preliminary injunction was consolidated with the determination of the suit on its merits. The case was submitted on affidavits, depositions, and memoranda of law; no oral testimony was taken. On July 21, 1976, the Superior Court upheld Alaska Hire in its entirety and denied appellants all relief. On appeal, the Alaska Supreme Court unanimously held that Alaska Hire's one-year durational residency requirement was unconstitutional under both the state and federal Equal Protection Clauses, 565 P. 2d 159, 165 (1977), and held further that a durational residency requirement in excess of 30 days was constitutionally infirm. Id., at 171. By a vote of 3 to 2, however, the court held that the Act's general preference for Alaska residents was constitutionally permissible. Appellants appealed the State Supreme Court's judgment insofar as it embodied the latter holding, and we noted probable jurisdiction. 434 U. S. 919 (1977). We reverse.

5 Section 38.40.090 provides:

"In this chapter

"(1) 'resident' means a person who

"(A) except for brief intervals, military service, attendance at an educational or training institution, or for absences for good cause, is physically present in the state for a period of one year immediately before the time his status is determined;

"(B) maintains a place of residence in the state;

"(C) has established residency for voting purposes in the state;

"(D) has not, within the period of required residency, claimed residency in another state; and

"(E) shows by all attending circumstances that his intent is to make Alaska his permanent residence."

• Appellees have not cross-appealed this portion of the Alaska Supreme Court's decision, which rests upon an independent and adequate state ground. Murdock v. Memphis, 20 Wall. 590 (1875).

Preliminarily, we hold that this case is not moot. Despite the Alaska Supreme Court's invalidation of the one-year durational residency requirement, a controversy still exists between at least five of the appellants-Tommy Ray Woodruff, Frederick A. Mathers, Emmett Ray, Betty Cloud, and Joseph G. O'Brien and the state appellees. These five appellants have all sworn that they are not residents of Alaska, Record 43, 47, 49, 96, 124. Therefore, none of them can satisfy the element of the definition of "resident" under § 38.40.090 (1) (D) that requires that an individual "has not, within the period of required residency, claimed residency in another state." They thus have a continuing interest in restraining the enforcement of Alaska Hire's discrimination in favor of residents of that State."

Appellants' principal challenge to Alaska Hire is made under the Privileges and Immunities Clause of Art. IV, § 2: "The Citizens of each State shall be entitled to all Privileges and Immunities of Citizens in the several States." That provision, which "appears in the so-called States' Relations Article, the same Article that embraces the Full Faith and Credit Clause, the Extradition Clause the provisions for the admission of new States, the Territory and Property Clause, and the Guarantee Clause," Baldwin v. Montana Fish and Game Comm'n, 436 U. S. 371, 379 (1978), "establishes a norm of comity," Austin v. New Hampshire, 420 U. S. 656, 660 (1975), that is to prevail among the States with respect to their treat

... "

'As to the remaining three appellants-Sidney S. Hicklin, Ruby E. Dorman, and Harry A. Browning-the case does appear moot. At the time this suit was instituted, all three claimed to be Alaskan residents, but none had lived in the State continuously for one year. Record 45, 51–52, 126-127. Consequently, the only aspect of Alaska Hire they challenged was the Act's one-year durational residency requirement. When this requirement was held invalid by the Alaska Supreme Court, their controversy with the appellees seems to have terminated.

ment of each other's residents. The purpose of the Clause, as described in Paul v. Virginia, 8 Wall. 168, 180 (1869), is

"to place the citizens of each State upon the same footing with citizens of other States, so far as the advantages resulting from citizenship in those States are concerned. It relieves them from the disabilities of alienage in other States; it inhibits discriminating legislation against them by other States; it gives them the right of free ingress into other States, and egress from them; it insures to them in other States the same freedom possessed by the citizens of those States in the acquisition and enjoyment of property and in the pursuit of happiness; and it secures to them in other States the equal protection of their laws. It has been justly said that no provision in the Constitution has tended so strongly to constitute the citizens of the United States one people as this."

Appellants' appeal to the protection of the Clause is strongly supported by this Court's decisions holding violative of the Clause state discrimination against nonresidents seeking to ply their trade, practice their occupation, or pursue a common calling within the State. For example, in Ward v. Maryland, 12 Wall. 418 (1871), a Maryland statute regulating the sale of most goods in the city of Baltimore fell to the privileges and immunities challenge of a New Jersey resident against whom the law discriminated. The statute discrimi

8 Although this Court has not always equated state residency with state citizenship, compare Travis v. Yale & Towne Mfg. Co., 252 U. S. 60, 78–79 (1920), and Blake v. McClung, 172 U. S. 239, 246-247 (1898), with Southern R. Co. v. Mayfield, 340 U. S. 1, 3-4 (1950); Douglas v. New Haven R. Co., 279 U. S. 377, 386-387 (1929); and La Tourette v. McMaster, 248 U. S. 465, 469-470 (1919), it is now established that the terms "citizen" and "resident" are "essentially interchangeable," Austin v. New Hampshire, 420 U. S. 656, 662 n. 8 (1975), for purposes of analysis of most cases under the Privileges and Immunities Clause of Art. IV, § 2. See Toomer v. Witsell, 334 U. S. 385, 397 (1948).

nated against nonresidents of Maryland in several ways: It required nonresident merchants to obtain licenses in order to practice their trade without requiring the same of certain similarly situated Maryland merchants; it charged nonresidents a higher license fee than those Maryland residents who were required to secure licenses; and it prohibited both resident and nonresident merchants from using nonresident salesmen, other than their regular employees, to sell their goods in the city. In holding that the statute violated the Privileges and Immunities Clause, the Court observed that "the clause plainly and unmistakably secures and protects the right of a citizen of one State to pass into any other State of the Union for the purpose of engaging in lawful commerce, trade, or business without molestation." Id., at 430. Ward thus recognized that a resident of one State is constitutionally entitled to travel to another State for purposes of employment free from discriminatory restrictions in favor of state residents imposed by the other State.

Again, Toomer v. Witsell, 334 U. S. 385 (1948), the leading modern exposition of the limitations the Clause places on a State's power to bias employment opportunities in favor of its own residents, invalidated a South Carolina statute that required nonresidents to pay a fee 100 times greater than that paid by residents for a license to shrimp commercially in the three-mile maritime belt off the coast of that State. The Court reasoned that although the Privileges and Immunities Clause "does not preclude disparity of treatment in the many situations where there are perfectly valid independent reasons for it," id., at 396, "[i]t does bar discrimination against citizens of other States where there is no substantial reason for the discrimination beyond the mere fact that they are citizens of other States." Ibid. A "substantial reason for the discrimination" would not exist, the Court explained, "unless there is something to indicate that noncitizens constitute a peculiar source of the evil at which the

[discriminatory] statute is aimed." Id., at 398. Moreover, even where the presence or activity of nonresidents causes or exacerbates the problem the State seeks to remedy, there must be a "reasonable relationship between the danger represented by non-citizens, as a class, and the . . . discrimination practiced upon them." Id., at 399. Toomer's analytical framework was confirmed in Mullaney v. Anderson, 342 U. S. 415 (1952), where it was applied to invalidate a scheme used by the Territory of Alaska for the licensing of commercial fishermen in territorial waters; under that scheme residents paid a license fee of only $5 while nonresidents were charged $50.

Even assuming that a State may validly attempt to alleviate its unemployment problem by requiring private employers within the State to discriminate against nonresidents an assumption made at least dubious by Wardit is clear that under the Toomer analysis reaffirmed in Mullaney, Alaska Hire's discrimination against nonresidents cannot withstand scrutiny under the Privileges and Immunities Clause. For although the statute may not violate the Clause if the State shows "something to indicate that noncitizens constitute a peculiar source of the evil at which the statute is aimed," Toomer v. Witsell, supra, at 398, and, beyond this, the State "has no burden to prove that its laws are not violative of the... Clause," Baldwin v. Montana Fish and Game Comm'n, 436 U. S., at 402 (BRENNAN, J., dissenting), certainly no showing was made on this record that nonresidents were "a peculiar source of the evil" Alaska Hire was enacted to remedy, namely, Alaska's "uniquely high unemployment." Alaska Stat. Ann. § 38.40.020 (1977). What evidence the record does contain indicates that the major cause of Alaska's high unemployment was not the influx of nonresidents seeking employment, but rather the fact that a substantial number of Alaska's jobless residents-especially the unemployed Eskimo and Indian residents-were unable to 9 Cf. Edwards v. California, 314 U. S. 160 (1941).