The justices did temporarily uphold one provision, one that allows police officers in Arizona to check the immigration status of those they detain for other reasons. But support for the provision was highly conditional, and the provision will now be challenged in the lower courts.
The president said: "What this decision makes unmistakably clear is that Congress must act on comprehensive immigration reform. A patchwork of state laws is not a solution to our broken immigration system -- it's part of the problem."
The administration argued successfully that anti-illegal immigration laws in Arizona and other states usurped federal authority.
Obama said: "I remain concerned about the practical impact of the remaining provision of the Arizona law that requires local law enforcement officials to check the immigration status of anyone they even suspect to be here illegally. I agree with the court that individuals cannot be detained solely to verify their immigration status. ... Going forward, we must ensure that Arizona law enforcement officials do not enforce this law in a manner that undermines the civil rights of Americans, as the court's decision recognizes."
The president added, "I will work with anyone in Congress who's willing to make progress on comprehensive immigration reform that addresses our economic needs and security needs, and upholds our tradition as a nation of laws and a nation of immigrants."
Homeland Security Security Secretary Janet Napolitano, who oversees immigration law enforcement, said she was also pleased. She said the court's decision not to strike down one of the state law's provisions "at this time will make [her department's] work more challenging. Accordingly, [the department] will implement operational enhancements to its programs in Arizona to ensure that the agency can remain focused on its priorities."
Judicial Watch, a conservative legal group in Washington that filed a friend-of-the-court brief in the Supreme Court case, concentrated on the provision left in place.
Judicial Watch President Tom Fitton said: "This is a victory for the safety and security of Arizona and the nation. The Supreme Court held that local police can help to enforce immigration law by inquiring about immigration status. This sensible application of the law confirms that local law enforcement can use an additional tool to protect public safety. We can expect dozens of states to enact laws further empowering the police as Arizona did. The Obama administration should now focus on enforcing immigration laws rather than thwarting them."
Arizona Gov. Jan Brewer also praised the ruling as a "victory."
"Today's decision by the U.S. Supreme Court is a victory for the rule of law," she said on her official Web site. "It is also a victory for the 10th Amendment and all Americans who believe in the inherent right and responsibility of states to defend their citizens. After more than two years of legal challenges, the heart of [the state law] can now be implemented in accordance with the U.S. Constitution."
She added, "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."
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