PHOENIX — More than two years after it was signed into law, the most contentious part of Arizona's landmark immigration legislation is expected to go into effect following a federal court ruling issue late Wednesday.

But the U.S. Supreme Court laid a legal minefield that Arizona now must navigate when the critical provision takes effect. The clause, one of the few significant ones that the high court left standing in a June ruling, requires all Arizona police officers to check the immigration status of people they stop while enforcing other laws and suspect are in the country illegally.

While preserving that requirement, however, the Supreme Court explicitly left the door open to arguments that the law leads to civil rights violations. Attorneys would need actual victims to make that case.