Today, the Supreme Court of the United States made it much more difficult for Arizona to disenfranchise voters. In 2004, Arizona voters approved a law which required election officials to reject any voter registration that was not accompanied with proof of citizenship. The Supreme Court struck down that law, saying that the National Voter Registration Act of 1993 forbids states from demanding additional information beyond what the federal voter registration form requires.

According to the Voter Registration Act, states must “accept and use” the federal form for voter registration, which requires the potential voter to affirm they are a United States citizen, and they are over the age of 18. Arizona argued that the “accept and use” wording in the Act, only required a state to “receive” the federal form, not consider it as a valid registration. Justice Antonin Scalia wrote the court opinion, which stated “Determining what qualifications a voter must possess is the province of the States. Arizona is correct that it would raise serious constitutional doubts if a federal statute prevented a State from obtaining the information necessary to enforce its voter qualification. But to avoid those doubts it is not necessary to give “accept and use” a meaning that allows Arizona to deny sufficiency of the Federal Form.”

Justice Scalia did, however, write that Arizona could pursue a “proof of citizenship” measure, by requesting the Federal Election Assistance Commission include the requirement on the federal form. Scalia essentially said that if the Commission failed to act on Arizona's request, that state would have the grounds to bring another court challenge. For now, it appears that Arizona won't be able to disenfranchise voters by requiring additional citizenship documentation. However, it's doubtful that the Republican-led state will suddenly stop its efforts to keep as many voters as possible away from the polls.