It sounds a little like whack-a-mole on voter ID laws: After the Supreme Court told Arizona it could no longer require proof of citizenship for voters in federal elections, the state plans to employ a work-around of sorts. The Arizona Republic calls it a "dual-track voting system" and the New York Times a "two-tiered voting system." People who register to vote via the federal registration form will be able to vote only in federal races, while those who use the state form—which still requires proof of citizenship—can vote in local, state, and federal races.
The move exploits a loophole in the Supreme Court ruling, explains the Times. While it declared that states can't trump Congress when it comes to federal elections, it left open the ability for them to keep voter ID restrictions in place on state elections. Hence, the separate ballots for voters depending on how they registered, which has raised fears of a logistical nightmare on Election Day. Kansas actually made the move first, and the two states also are simultaneously suing the federal requirement to demand that the federal form require proof of citizenship. If they succeed, their dual-voting systems would then be scrapped.