Under U.S. v. Ptasynski, 462 U.S. 74 (1983), the imposition of different tax burdens in different places is suspect. While the Supreme Court’s review is relatively deferential, the clause does require that taxes apply “at the same rate, in all portions of the United States where the subject of the tax is found.” “Where Congress does choose to frame a tax in geographic terms,” on the other hand, the court “will examine the classification closely to see if there is actual geographic discrimination,” to see whether there are “neutral factors” that can justify the geographic distinction.

While I doubt the senators would be so brazen as to expressly include a geography-based exception in the final bill language, a statutory provision clearly motivated by a desire to, in the court’s words, “grant . . . an undue preference at the expense of other . . . states” could have problems. As Galle notes, “By this standard, the ‘Alaska Purchase’ looks like it’s in trouble.”