Page:Alabama v. North Carolina, 560 U.S. (2010) slip opinion.pdf/32

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quotation marks omitted); see also Cuyler v. Adams, 449 U. S. 433, 438 (1981) (“[C]ongressional consent transforms an interstate compact. . . into a law of the United States”).

From this principle, however, it simply does not follow that a law’s nature and origin as a compact must be dismissed as irrelevant. Like a treaty, a compact represents an agreement between parties. See New Jersey, supra, at 831 (SCALIA, J., dissenting) (“[T]he Compact here is of course a treaty”). The Court’s duty in interpreting a compact involves ascertaining the intent of the parties. See Sullivan v. Kidd, 254 U. S. 433, 439 (1921) (“[T]reaties are to be interpreted upon the principles which govern the interpretation of contracts . . . with a view to making effective the purposes of the high contracting parties”); Wright v. Henkel, 190 U. S. 40, 57 (1903) (“Treaties must receive a fair interpretation, according to the intention of the contracting parties”). Carrying out this duty may lead the Court to consult sources that might differ from those normally reviewed when an ordinary federal statute is at issue. That much is surely implicit in the Court’s reference to contract law principles elsewhere in its opinion in the instant case. See, e.g., ante, at 14 (“[T]he parties’ course of performance under the Compact is highly significant”); ibid. (citing the Restatement); id., at 18–19 (same); see also New Jersey, supra, at 830–831 (SCALIA, J., dissenting) (construing a compact in light of “hornbook contracts law that the practical construction of an ambiguous agreement revealed by later conduct of the parties is good indication of its meaning”).

That said, it is quite correct to hold here that the reasonable expectations of the contracting States, as manifested in the Compact, do not reveal an intent to limit North Carolina’s power of withdrawal. For purposes of rejecting this argument, it is sufficient to note—as the Court does—that the Compact permits any State to