Arizona v. Inter Tribal Council of Arizona went before the Supreme Court Monday. Arizona passed a law requiring proof of citizenship to register to vote in 2004 which conflicts with the National Voter Registration Act passed in 1993 that does not require proof of citizenship to register to vote.

From SCOTUS Blog

At the center of the case is an Arizona law, approved by the state’s voters nine years ago, that requires a would-be voter seeking to register to show proof of U.S. citizenship as an additional requirement besides submitting a federal form which includes a question — enforced by possible perjury prosecution — asking whether or not one is a citizen.

Justice Antonin Scalia, who started out in the argument by criticizing Arizona for not filing the right kind of legal challenge, set the tone for the rest of the argument by trying to pry out of three lawyers what the difference is between “may only require” and “shall.”  The federal “motor voter” law, seeking to streamline the process of signing up to vote, mandates a federal form and puts supposedly strict limits on states’ ability to add other requirements.  It says that they may use some ways to verify a claim of voter eligibility, but “may require only” a short list of added information — and proof of citizenship is not one of those things.

Justice Alito supported Scalia’s position but the one everyone watches is the swing vote, Justice Kennedy.

Kennedy, who might well have the controlling vote, in view of how the overall argument went, at one point showed some skepticism about states’ power — under the federal registration law — to add complicating requirements to the registration regime.  A simple postcard method of registration, the Justices noted, was intended by Congress to be “presumptive evidence” that a person was eligible to register, and adding other requirements could mean that “the whole utility of this single form is gone.”

During the arguments Justices Sotomayor and Scalia represented the different sides of the division in the court. Scalia hinted at wanting a broader challenge of the National Voter Registration Act while Sotomayor said the purpose of the NVR was to simplify voter registration, a process that according to her the Arizona’s law complicates.