On Monday, the U.S. Supreme Court struck down an Arizona law requiring proof of citizenship as part of voter registration applications. The Arizona statute conflicted with a federal law requiring states to accept application only signed statements affirming voter eligibility.

In a rare 7-2 decision, the court ruled the federal law preempted the Arizona law, with conservative Justice Antonin Scalia writing the majority opinion, joined by the liberal justices, as well as fellow conservative Chief Justice John Roberts and moderate Anthony Kennedy.

While the court seems in general agreement, the ruling has been contentious among groups on Capitol Hill, particularly amid the Senate's current debate on its comprehensive immigration reform bill.

"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, of the group Voting Rights Project at the American Civil Liberties Union. "In doing so, the court has taken a vital step in ensuring the ballot remains free, fair, and accessible for all citizens."

"Today's U.S. Supreme Court decision is a victory for Latinos and all voters," said the National Association of Latino Elected and Appointed Officials, pointing to the deleterious effect the Arizona law has had on the state's Hispanic population over the last seven years.

"Thousands of voters were inappropriately affected by Arizona's effort, which made it significantly more difficult for Latinos, naturalized citizens and other underrepresented groups to register to vote. These requirements had real consequences for the Latino electorate in the state, with Arizona election officials rejecting a disproportionately higher number of registration applications from Latinos than other voting groups since the law's enactment in 2004," said NALEO.

But supporters of the statute lashed out at the court's decision. ""I believe we must go out of our way to protect the integrity of America's elections, to avoid the fraud we see regularly in other nations, and which if not checked will rise up here in the United States," said Russell Pearce, a former Arizona legislator who helped pass the law in 2004. "It ought to be common sense that proof of citizenship be required for voter registration, especially given the concrete evidence we've seen that illegal aliens are indeed both registered and voting. But common sense and America's judicial system don't always see eye to eye, and this is one area we'll just have to keep working."

Despite charges from conservatives, there is no evidence of widespread voter fraud in the United States, and instances of attempted fraud number in the double digits nationwide, an insignificant portion of the tens of millions of votes cast.