Opinion of the Court
way. See App. 10a–26a; App. to Pet. for Cert. 55a. As the director explained, Cougar Den owed the tax because Cougar Den had caused fuel to enter “into this [S]tate at the Washington–Oregon boundary on the Highway 97 bridge” by means of a “tank truck” destined for “the Yakama Reservation.” Ibid. The director offers this explanation in addition to quoting the quantity of fuel that Cougar Den possessed because the element of travel by ground transportation is a necessary prerequisite to the imposition of the tax. Put another way, the State must prove that Cougar Den traveled by highway in order to apply its tax.
B
We are not convinced by the arguments raised to the contrary. The Department claims, and The Chief Justice agrees, that the state tax has little or nothing to do with the treaty because it is not a tax on travel with fuel but rather a tax on the possession of fuel. See Brief for Petitioner 26–28; post, at 5 (dissenting opinion).
We cannot accept that characterization of the tax, however, for the Washington Supreme Court has authoritatively held that the statute is a tax on travel. The Washington Supreme Court held that the Washington law at issue here “taxes the importation of fuel, which is the transportation of fuel.” 188 Wash. 2d, at 69, 392 P. 3d, at 1020. It added that “travel on public highways is directly at issue because the tax [is] an importation tax.” Id., at 67, 392 P. 3d, at 1019. In so doing, the State Supreme Court heard, considered, and rejected the construction of the fuel tax that the Department advances here. See ibid., 392 P. 3d, at 1019 (“The Department argues, and the director agreed, that the taxes are assessed based on incidents of ownership or possession of fuel, and not incident to use of or travel on the roads or highways…. The Department’s argument is unpersuasive…. Here, travel
