The Supreme Court will decide whether an Arizona law that requires voters to present identification before voting proving they are U.S. citizens is constitutional.

The requirement is part of Proposition 200, a law approved by Arizona voters in 2004, which tied a host of benefits and rights to proof of citizenship, including some government benefits. The voter identification provision of Proposition 200 was challenged and blocked by the Ninth Circuit Court of Appeals which held that federal election law preempts Arizona’s identification requirement. Federal law allows voters to fill out a mail-in voter registration card and swear they are citizens under penalty of perjury. Federal law does not require an additional showing of proof of citizenship, but the 2004 Arizona law does.

The Ninth Circuit’s ruling applies only to those who register using the federal mail-in form. Arizona has its own separate form and online system to register to vote and the Ninth Circuit ruling doesn’t affect proof of citizenship requirements using the state forms.

That means the Supreme Court review will touch on this issue of federalism and not the broader question of whether Arizona can tie proof of citizenship to voting and receipt of state benefits generally. And because the Ninth Circuit decision blocked the 2004 law from going into effect and because the Court will not rule on the case until after this year’s election, the requirement will not be in effect come November 6th.