David H. Gans has this persuasive essay about why the entire Federal Voting Rights Act is constitutional. The language of the 15th amendment forms the basis for this opinion. Thanks to Rick Hasen for the link.
The statement in the referenced article – that the Constitution does not provide explicit language for equal treatment among the states – is true. Indeed, there not being an explicit statement allows Congress to enforce the 15th Amendment in a manner that discriminates among the states. But, inherent in the name “United States” is that the the United States consists of an inviable union of inviable states (Texas v. White). Accordingly, there should be a compelling reason for this extra scrutiny, as it compromises the integrity of the states.
Furthermore, I think the plaintiffs essentially concede that the Congress can discriminate among the states to protect voting rights if there is a compelling reason, in that they argue that the original circumstances warranting the VRA have changed.
I have a different take. Already in the Voting Rights Act is the answer.
“Under the Voting Rights Act, Section 4 of the act provides that a covered jurisdiction may seek to “bail out,” or remove itself from such coverage, and therefore be exempted from the preclearance requirements, by seeking a declaratory judgment before a three-judge panel in U.S. District Court for the District of Columbia. A bailout judgment can be issued only if the court determines that the jurisdiction meets certain eligibility requirements for bailout contained in the statute, including a 10-year record of nondiscrimination in voting-related actions. The act also provides that the attorney general can consent to entry of a judgment of bailout only if, based upon investigation, the attorney general is satisfied that the jurisdiction meets the eligibility requirements.”
Also in the act, voters can use the reverse of Section 4 and ask the court, with convincing documentation, to implement preclearance.