Today, the Supreme Court agreed to hear Arizona v. Inter Tribal Council, a challenge to Arizona Proposition 200, which requires prospective voters to show proof of citizenship when registering to vote.

Like a litany of other states, Arizona passed this common-sense reform to prevent noncitizens from illegally voting in elections and to ensure the integrity of its elections.

Proposition 200 provides that state election officials “shall reject any application for registration that is not accompanied by satisfactory evidence of United States citizenship.” Such evidence includes a driver’s license, a photocopy of a birth certificate or passport, naturalization documents, or “other documents that are meant as proof that [may be] established pursuant to” federal immigration laws. Not long after its passage, Proposition 200 was challenged in federal court.

This case has a thorny procedural history going back to 2006, including a district panel decision by retired Supreme Court Justice Sandra Day O’Connor and some questionable tactics by the Eric Holder Justice Department, but two issues are presently before the Supreme Court. First, the justices will examine whether the Ninth Circuit Court of Appeals erroneously created a new form of heightened preemption pursuant to the Elections Clause of the U.S. Constitution that purportedly applies to state voting laws. Second, the Court will assess whether the National Voter Registration Act (NVRA) preempts Proposition 200.

The Ninth Circuit found that when evaluating whether federal law supersedes a state voting requirement, the normal rules of preemption, such as the traditional presumption against preemption and the plain statement rule, do not apply because the states “have no reserved authority over the domain of federal elections.” This discounts the Supreme Court’s repeated finding that the Elections Clause gives states “broad power” regarding procedural mechanisms for administering elections.

Proposition 200 should stand unless it is preempted by some countervailing federal law, such as the NVRA. The NVRA, passed in 1993, sets forth procedures for states to increase the number of registered voters. It requires states to “accept and use” federal voter registration applications submitted through the mail but authorizes states to “require … such identifying information … as is necessary to … assess the eligibility of the applicant.”

Thus, whether or not the NVRA preempts Proposition 200 turns on if Congress’s command that states “accept and use” a federal form can be interpreted to enable states to request additional information—including proof of citizenship. The Ninth Circuit’s cramped reading of the NVRA would effectively require Arizona to accept voter registration applications on an honor system.

Following the Supreme Court’s decision in another Arizona preemption case last term, it is anyone’s guess how the justices’ votes will shake out in this latest case.