If the Supreme Court strikes down President Obama's overhaul of the health-care system, the controversial decision could erode the court's reputation as an impartial arbiter, critics say.

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he Supreme Court struck down key parts of Arizona's controversial immigration law on Monday — saying the rules were pre-empted by federal law — while upholding a central provision allowing police officers to ask for the papers of suspected illegal immigrants stopped for separate crimes. After Arizona Gov. Jan Brewer signed the law, known as SB1070, in 2010, several states used it as a blueprint for their own harsh immigration rules, spurring the Justice Department to file a legal challenge. The Supreme Court vote was 5-3, with Justice Elena Kagan recusing herself, as she "oversaw the federal government's role in the case as Solicitor General" before joining the court. Also on Monday, the court overturned a Montana campaign finance law limiting corporate donations, and ruled that juveniles cannot be sentenced to life in prison without the possibility of parole. The court did not rule on the constitutionality of ObamaCare. A decision on that case is expected Thursday.