In a 2004 ballot initiative, Arizona voters decided that they wanted their state to go one step further on the  requirements of a 1993 federal law that allows people to register to vote via a single form accepted by all the states, on which they must “swear” that they are citizens of the United States, by asking people to instead actually present documentary proof of citizenship like a birth certificate, passport, or tribal ID card before registering in order to prevent voter fraud.

The border state has been fighting to be allowed to ask for evidence of prospective voters’ citizenship ever since, but in a major decision released this morning, the Supreme Court struck down Arizona’s Proposition 200 as an attempt to override the federal “motor voter” law in a 7-2 ruling, with Justice Kennedy concurring and Justices Thomas and Alito dissenting:

A federal appeals court said that Arizona had gone too far and essentially rejected the federal form. Arizona said it was not a rejection of the federal form any more than asking for ID at an airport is a rejection of a plane ticket. …

At an oral argument in March, Thomas Horne, a lawyer for Arizona, told the justices that the state was within its rights to ask for additional information beyond the simple federal form.

“It’s extremely inadequate,” Horne said. “It’s essentially an honor system. It does not do the job.”

“Well,” answered Justice Sonia Sotomayor, “that’s what the federal system decided was enough.”

The court’s conservatives appeared sympathetic to the Arizona side. Scalia said that federal law clearly empowers the states to take additional action to assess a potential voter’s eligibility.

“Under oath is not proof at all,” he said. “It’s just a statement.”

Alabama, Georgia, and Kansas all have similar laws to Arizona’s proof-of-citizenship requirement and joined Arizona in their suit, and the Court’s ruling (written by Justice Scalia) pointed out that their next recourse action-item would be to petition the federal government to allow for state-specific instruction on the form and/or beef up the federal law altogether, and then go to court if the government declines to do so. …I’m going to go ahead and throw out a guess right now that the Obama administration would probably be disinclined to acquiesce to their request, for the very same reasons that so-called rights groups are pretty darn pleased about today’s decision:

“Today’s decision sends a strong message that states cannot block their citizens from registering to vote by superimposing burdensome paperwork requirements on top of federal law,” said Nina Perales, vice president of litigation for the Mexican American Legal Defense and Educational Fund and lead counsel for the voters who challenged Proposition 200. …

Opponents of Arizona’s law see it as an attack on vulnerable voter groups such as minorities, immigrants and the elderly. They say they’ve counted more than 31,000 potentially legal voters in Arizona who easily could have registered before Proposition 200 but were blocked initially by the law in the 20 months after it passed in 2004. They say about 20 percent of those thwarted were Latino.

Barbara Arnwine, president and executive director of the Lawyers’ Committee for Civil Rights Under Law, called the decision a victory. “The court has reaffirmed the essential American right to register to vote for federal election without the burdens of state voter suppression measures,” she said.