The U.S. Supreme Court ruled that Arizona can enforce a law requiring proof of citizenship for state voter registration, but not for federal elections, including presidential and mail-in voting. The decision, which was split 5-4, is seen as a partial victory for Republicans who argue it upholds election integrity. However, it does not affect those already registered to vote or using federal forms to register. The ruling follows ongoing legal battles and controversies over voting laws in Arizona, stemming from the 2020 presidential election. The case highlights the broader national debate over voter ID laws and election security.