Updated

The Supreme Court on Monday struck down much of Arizona's controversial immigration law, but it upheld for now a key provision that requires police officers to check the immigration status of those they suspect may be in the country illegally.

The provision on mandatory checks during routine stops will now kick back to a lower court for review and still could still be subject to challenge. The rest of the ruling, though, definitively strikes down three other provisions in the Arizona law.

Those provisions had made it a crime for immigrants to seek employment without work permits and to not carry their immigration papers, and they had allowed police to arrest anyone they suspect committed a deportable offense. Without the latter provision, the requirement to conduct routine immigration checks has little enforcement power behind it.

The court was unanimous in allowing the immigration checks to go forward, but divided on the rest. The decision now throws into question how other states that had followed Arizona's lead on immigration enforcement will proceed. In Washington, the Obama administration signaled a tough road ahead for those states by suspending a key enforcement program that allowed local officials to partner with federal agents in carrying out immigration law.

The court's decision Monday prompted a range of reactions from officials in Washington and Arizona.

More On This...

"This is a bit of a mixed bag," Rep. Jeff Flake, R-Ariz., told Fox News.

Some Democrats expressed concern about the remaining provision, while others declared outright victory. Sen. Chuck Schumer, D-N.Y., called the ruling "as strong a repudiation of the Arizona law as one could expect."

On the GOP side, a few lawmakers described the decision as disappointing, while keeping pressure on the Obama administration to fix the country's immigration system. Others saw a silver lining.

Among them was Arizona Gov. Jan Brewer, who put out an optimistic statement Monday, indicating the state would move to carry out the remaining law, even without the three other planks.

Brewer hailed the decision as a "victory for the rule of law" -- in reference to the one provision that was upheld. "After more than two years of legal challenges, the heart of SB 1070 can now be implemented in accordance with the U.S. Constitution," Brewer said.

President Obama, too, said he was "pleased" by the ruling.

"What this decision makes unmistakably clear is that Congress must act on comprehensive immigration reform," he said. "A patchwork of state laws is not a solution to our broken immigration system -- it's part of the problem."

Brewer said she expects legal challenges to the remaining provision of the law to continue. "Our critics are already preparing new litigation tactics in response to their loss at the Supreme Court, and undoubtedly will allege inequities in the implementation of the law," she said.

Brewer also cautioned her state's police officers against taking the policy too far, saying: "Law enforcement will be held accountable should this statute be misused in a fashion that violates an individual's civil rights."

The federal government had claimed the law encroached on its authority to enforce immigration law.

Justice Anthony Kennedy wrote the opinion, which was released Monday, on behalf of the majority. Kennedy was joined by Chief Justice John Roberts and Justices Stephen Breyer, Ruth Bader Ginsburg and Sonia Sotomayor.

On the immigration checks provision, Kennedy wrote that "uncertainty" over how that policy would be carried out prevent the court from assuming it would conflict with federal law. "As a result, the United States cannot prevail in its current challenge," Kennedy wrote.

But he offered words of warning pertaining to the rest of the law.

"Arizona may have understandable frustrations with the problems caused by illegal immigration while that process continues, but the State may not pursue policies that undermine federal law," Kennedy wrote. The justice also noted that "discretion in the enforcement of immigration law embraces immediate human concerns," and also "involve(s) policy choices that bear on this Nation's international relations."

He added: "The pervasiveness of federal regulation does not diminish the importance of immigration policy to the States. Arizona bears many of the consequences of unlawful immigration."

The Supreme Court is currently wrapping up its term. The public is still awaiting a landmark decision on the federal health care overhaul, which is expected to be released on Thursday.

Click here to read the immigration ruling.