The U.S. Supreme Court case Arizona, et al., v. The Inter Tribal Council of Arizona, Inc., et al., 2012 revolved around the issue of voter registration requirements in the state of Arizona. Specifically, it questioned whether a state could require proof of citizenship beyond what was required by federal law for voter registration purposes. In this case, an Arizona law required individuals to show evidence of their citizenship before they could register to vote - a requirement that went beyond what was mandated by the Federal Form developed under the National Voter Registration Act (NVRA). The Inter Tribal Council and other groups challenged this law as being preempted by federal legislation. In its decision issued in 2013, the Supreme Court ruled against Arizona stating that states cannot impose additional requirements on top of those set out in federal laws regarding voter registration for federal elections; hence striking down such provisions from Proposition 200 passed by voters in 2004.

In the dissenting opinion for Arizona v. The Inter Tribal Council of Arizona, Inc., Justice Clarence Thomas argued that states have the authority to determine qualifications for voters in federal elections, as long as they do not conflict with constitutional amendments or federal law. He disagreed with the majority's interpretation of the National Voter Registration Act (NVRA), stating that it does not preclude a state from requiring additional information to verify voter eligibility beyond what is required by NVRA’s Federal Form. He also contended that if Congress intended to prevent states from asking for proof of citizenship, it would have explicitly stated so in the legislation. Therefore, he believed Arizona's requirement for proof of citizenship did not violate NVRA and should be upheld.