The Supreme Court ruled on Monday that an Arizona law requiring proof of U.S. citizenship for prospective voters was pre-empted by federal law, landing another blow against state policies derided as targeting immigrants.

In a 7-2 ruling (PDF) delivered by Justice Antonin Scalia, the high court decided that the National Voter Registration Act (NVRA), passed in 1993, took precedence over Arizona's Proposition 200, a 2004 law that allowed election officials to turn away voters who did not provide proof of citizenship on top of the voter registration form mandated by the NVRA.

"This decision reaffirms the principle that states may not undermine this critical law's effectiveness by adding burdens not required under federal law," said Laughlin McDonald, special counsel for the American Civil Liberties Union (ACLU), in a statement. "In doing so, the court has taken a vital step in ensuring the ballot remains free, fair, and accessible for all citizens."

The federal form requires prospective voters to check "yes" or "no" when asked if they are U.S. citizens, and to sign the form confirming their response under penalty of perjury. Arizona's mandate required applicants without driver's licenses to also submit documents such as a state-issued identification card, passport, a birth certificate or proof of naturalization to demonstrate their voting status.

"It would raise serious constitutional doubts if a federal statute precluded a State from obtaining the information necessary to enforce its voter qualifications," Scalia wrote in the decision. "The NVRA can be read to avoid such a conflict, however."

SCOTUSBlog reported that a state provision requiring voters to bring identification to the polls was not struck down, and that the ruling opened the door for Arizona to ask the federal Election Assistance Commission to include more stringent citizenship requirements in the NVRA form and possibly issue its own legal challenge should the commission refuse to do so.

According to NBC News, Thomas Horne, who represented the state in the case, argued before the justices in March that the NVRA was inadequate.

"It's essentially an honor system," Horne told the court. "It does not do the job."

However, Patricia A. Millett, who represented the Inter Tribal Council of Arizona and other groups challenging the law, countered that statements made under oath "are proof beyond a reasonable doubt" in criminal cases involving the death penalty.

"Voters scored a huge victory today," said Wendy Weiser, director of the democracy program for the Brennan Center for Legal Justice, in a statement. "We applaud the Supreme Court for confirming Congress' power to protect the right to vote in federal elections. Congress recognized that voter registration must be made more accessible when it passed the National Voter Registration Act, and the court also affirmed that today."

Three other states with similar voting laws, Alabama, Georgia and Kansas, joined Arizona in urging the high court to uphold Proposition 200's requirements for applicants. Justices Samuel Alito and Clarence Thomas filed separate dissenting opinions.

Monday's ruling was delivered nearly a year to the day the court struck down most of Arizona's SB1070, which was also critized for being anti-immigrant.

Update, 3:02 p.m. EST: The executive director of an immigration advocacy group,, praised the court's decision in an email to The Raw Story Monday.

This ruling should once and for all end the dangerous and wasteful practice of phony 'get-tough' laws that target immigrants in states like Arizona and which are currently being debated in Congress," Arturo Carmona said. "We should be finding ways to support immigrants as they contribute to their communities instead."

[Image: "Ventura Country, CA - November 06: Voters At Polling Station In 2012 Presidential Election On November 06, 2012 Ventura County, CA" by Spirit of America via]