Justice Ginsburg says the "equal sovereignty" principle "is capable of much mischief" and brainstorms ideas for vexatious litigation.

In her dissenting opinion in Shelby County v. Holder (PDF), she frets about all the federal laws that treat states differently from each other and could be subjected to attacks based on the majority's "fundamental principle of equal sovereignty" among the states:

See, e.g., 28 U. S. C. §3704 (no State may operate or permit a sports-related gambling scheme, unless that State con­ducted such a scheme “at any time during the period beginning January 1, 1976, and ending August 31, 1990”); 26 U. S. C. §142(l) (EPA required to locate green building project in a State meeting specified population criteria); 42 U. S. C. §3796bb (at least 50 percent of rural drug enforcement assistance funding must be allocated to States with “a population density of fifty-two or fewer persons per square mile or a State in which the largest county has fewer than one hundred and fifty thousand people, based on the decennial census of 1990 through fiscal year 1997”); §§13925, 13971 (similar population criteria for funding to combat rural domestic violence); §10136 (specifying rules applicable to Nevada’s Yucca Mountain nuclear waste site, and providing that “[n]o State, other than the State of Nevada, may receive financial assistance under this sub­section after December 22, 1987”). 

It seems to me that the "equal sovereignty" principle is an important structural safeguard in the federal legislative process, protecting us from the democratic dysfunctions of things like the "Cornhusker Kickback." This is exactly the sort of thing that ought to shake judges out of the usual deference to Congress.