In striking down most of Arizona's immigration law, the U.S. Supreme Court sent the clear message that it is the constitutional responsibility of the federal government to regulate immigration. The nation cannot have 50 states with 50 different rules and standards for the regulation and enforcement of immigration law, undermining federal regulation in the process, the majority of justices concluded.

And while we are concerned that the Supreme Court let stand the law requiring police in Arizona to determine the immigration status of people they stop or arrest, we acknowledge that the court's 8-0 decision on that issue was well reasoned and sufficiently narrow.

Despite the split nature of the ruling, this was clearly a victory for the Obama administration and more importantly provided constitutional clarity that states cannot dictate through state laws the federal government's immigration priorities and policies.

Struck down on a 5-3 vote was the Arizona law that would have allowed state and local police to arrest people without a court warrant if officers concluded an individual's actions, status or conduct made them subject to deportation under federal law. Also found unconstitutional by the same margin was the attempt to make it a state crime in Arizona for immigrants without proper federal documentation to seek or hold jobs.

Finally, on a 6-2 vote, the court tossed a provision making it a state crime for an immigrant to fail to register with the federal government.

As troublesome as it may turn out to be, the Supreme Court made a good case that there is no constitutional barrier to the Arizona law ordering its officers to demand documentation of legal status if they have reason to suspect a person they have stopped for an infraction or arrest may be in the country illegally. State law enforcement authorities always had the right to ask about immigration status. The only change is the mandate that they do so, which does not appear to cross a constitutional barrier.

But this policy does carry a significant potential for abuse. Exactly what will raise suspicion of illegal status - skin color, surname, an accent? In writing the majority opinion, Justice Anthony M. Kennedy said Monday's decision does not preclude future constitutional challenges if evidence arises that the Arizona or similar laws are leading to violations of civil rights.

Civil rights groups say they will be watching closely, and so too will be federal authorities. Attorney General Eric H. Holder Jr. promised to "continue to vigorously enforce federal prohibitions against racial and ethnic discrimination."

We await a similar assurance from Mitt Romney, the Republican presidential candidate, that if elected his administration would do likewise.