PHOENIX — Barred by the Supreme Court from requiring proof of citizenship for federal elections, Arizona is complying — but setting up a separate registration system for local and state elections that will demand such proof.

The state this week joined Kansas in planning for such a two-tiered voting system, which could keep thousands of people from participating in state and local elections, including next year’s critical cycle, when top posts in both states will be on the ballot.

The states are using an opening left in June by the United States Supreme Court when it said that the power of Congress over federal elections was paramount but did not rule on proof of citizenship in state elections. Such proof was required under Arizona’s Proposition 200, which passed in 2004 and is one of the weapons in the border state’s arsenal of laws enacted in its battle against illegal immigration.

The two states are also jointly suing the federal Election Assistance Commission, arguing that it should change the federal voter registration form for their states to include state citizenship requirements. While the agency has previously denied such requests, the justices said the states could try again and seek judicial review of those decisions.