By Sahil Kapur

Voting rights advocates are sounding the warning sirens as the Supreme Court hears oral arguments Monday on a low-profile but important case on whether states may require people to submit proof of citizenship when registering to vote.

At issue is whether the Arizona law, known as Proposition 200, violates a federal law that requires states to let people register to vote while renewing drivers licenses or applying for social services. The form provided by the National Voter Registration Act requires people to attest that they are U.S. citizens, but not to provide documented proof, like the Arizona law does.

“If Arizona’s brazen attempt to evade the mandates of the NVRA is upheld, it will make it tougher for voters in Arizona to register, and other states with legislatures that are looking to suppress the vote will surely try to pass copycat legislation,” said Doug Kendall, president of the liberal-leaning Constitutional Accountability Center. “If the Court accepts Arizona’s most sweeping arguments against the NVRA, its ruling could severely limit Congress’ power to protect the right of Americans to register to vote.”

Rick Hasen, an election law expert and professor at UC-Irvine School of Law, told TPM that the “implications of this sleeper case could be profound.”

“If the Court holds that Arizona does not have to accept the federal form for voter registrations, it could have a major effect on the power of the federal government to impose rules on states for running congressional elections,” Hasen said in an email.

The challengers will argue that Prop 200 violates the NVRA by creating an unlawful burden for people to register to vote. Arizona will counter that its law, enacted by voters in 2004 in an effort to prohibit illegal immigrants from voting, is permissible under the NVRA. Arizona says the Constitution does not let Congress pre-empt nondiscriminatory voting laws in states.

“In sum,” Arizona writes in its brief, “this Court should find that the NVRA does not preempt Proposition 200’s evidence-of-citizenship requirement to avoid the serious constitutional question of whether, as so applied, it intrudes upon the States’ power under the Voter Qualifications Clauses to define and enforce voter qualifications in federal elections.”

Opponents of Prop 200 want to draw more attention to the case, which comes as the high court also considers overturning a centerpiece of the Voting Rights Act. Unlike the pending VRA case, however, the Prop 200 case is not about discrimination in voting laws, but rather about whether requiring proof of citizenship is too burdensome.

“Our Constitution grants Congress the power to pass legislation which makes our federal elections freer, fairer, and more accessible,” said Myrna Pérez, senior counsel at the liberal-leaning Brennan Center For Justice. “If that authority is undermined, voters could lose protections that are necessary and commonplace in today’s world.”