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In a surprise, the Supreme Court today struck down three of four provisions of Arizona's controversial immigration law --SB 1070.

Left standing by the High Court, however, was the "show me your papers" provision of the law requiring state and local police to perform roadside immigration checks if a "reasonable suspicion" exists that someone is in the country illegally.

The court essentially weighed whether in passing its own immigration law, Arizona was overstepping its bounds in what traditionally has been a federal matter. Arizona lawmakers said that the federal government had failed in its responsibility to secure the borders and control illegal immigration, and that states -- particularly those on the border -- were forced to deal with the consequences of people living here unlawfully and usurping state resources.

An estimated 11 million people live in the United States illegally -- most of them are Latinos and roughly half are visa overstays.

Arizona's move toward implementing its own immigration law set in motion similar efforts by lawmakers in other states frustrated by illegal immigration. But while some voted on and passed measures seeking to drive out undocumented immigrants, other states put their measures on hold, concerned about overwhelming legal challenges.

Removal [of an undocumented immigrant] is a civil matter, and one of its principal features is the broad discretion exercised by immigration officials, who must decide whether to pursue removal at all

— U.S. Supreme Court, in its written decision on Arizona's SB 1070

In this case, however, the court in its decision indicated that this provision would face further scrutiny.

The decision noted the complexity of immigration, and the discretion that federal officials must often exercise in determining how to deal with an undocumented person.

"Removal is a civil matter, and one of its principal features is the broad discretion exercised by immigration officials, who must decide whether to pursue removal at all," the decision said. "By authorizing state and local officers to make warrantless arrests of certain aliens suspected of being removable, Section 6 too creates an obstacle to federal law. As a general rule, it is not a crime for a removal alien to remain in the United States."

"Discretion in the enforcement of immigration law embraces immediate human concerns," said the decision. "Unauthorized workers trying to support their families, for example, likely pose less danger than alien smugglers or aliens who commit a serious crime. The equities of an individual case may turn on many factors, including whether the alien has children born in the United States, long ties to the community, or a record of distinguished military service."

Detaining people just on suspicion of unlawful immigration status, the court said, "would raise constitutional concerns…. And it would disrupt the federal framework to put state officers in the position of holding aliens in custody for possible unlawful presence without federal direction and supervision.”

At the same time, the Supreme Court noted that states bear the burden of problems that may be caused by a broken immigration system.

"The pervasiveness of federal regulations does not diminish the importance of immigration policy to the States," the court said. "Arizona bears many of the consequences of unlawful immigration. Hundreds of thousands of deportable aliens are apprehended in Arizona each year...Unauthorized aliens who remain in the State comprise, by one estimate, almost six percent of the population."

"Accounts in the record suggest there is an 'epidemic of crime, safety risks, serious property damage, and environmental problems' associated with an the influx of illegal migration across private land near the Mexican border," the court said.

Since passage in 2010, Arizona's SB1070, has become both a flashpoint for the national debate over immigration and enforcement. The law served as a blueprint for similar laws in other states, including Alabama, Georgia, Indiana, South Carolina and Utah. Courts have blocked implementation of parts of those states' laws pending a decision by the Supreme Court on Arizona's measure.

It also sealed the issue of immigration as an election-year issue, prompting both President Obama and the GOP presidential nominees to take positions on Arizona's law -- they nearly all supported it -- during the extended primary. At one point during the primary, Mitt Romney, now the expected GOP presidential nominee, drew fire when he described Arizona's law as a national model.

Later, Romney -- whose support of Arizona's law and hard line positions on immigration have aliented many Latinos -- said he had not meant that all of SB 1070 was a national model, just its E-Verify component, which requires employers to make sure their workers are eligible to work in the United States.

President Obama praised the High Court's rejection of most of the provisions it had reviewed, but expressed concern over the one the justices left intact.

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

"No American should ever live under a cloud of suspicion just because of what they look like," the President said. "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...What makes us American is not a question of what we look like or what our names are."

Two hours after the Supreme Court released its decision, Romney called it evidence of a failure of the Obama administration "to provide any leadership on immigration."

“Today's decision underscores the need for a President who will lead on this critical issue and work in a bipartisan fashion to pursue a national immigration strategy."

"Each state has the duty--and the right--to secure our borders and preserve the rule of law, particularly when the federal government has failed to meet its responsibilities," Romney said in a statement. "As Candidate Obama, he promised to present an immigration plan during his first year in office.  But four years later, we are still waiting.”

Soon after its passage in 2010, critics of SB 1070, including Latino rights organizations who feared profiling as a result of the enforcement measures, called for a business boycott of Arizona in protest.

The U.S. Department of Justice lawsuit seeking an injunction against enforcement of the law argued that immigration law was a federal prerogative.

Critics of the law condemned the Suprme Court decision.

In Washington D.C., a coalition of civil and immigrants rights groups announced a nationwide voter mobilization drive aimed at voting out of office any lawmaker who supported SB 1070. The groups include the National Association For the Advancement of Colored People (NAACP), the Service Employees International Union (SEIU), the Campaign for Community Change and the Arizona Dream Act Coalition.

“Today’s ruling marks a dark day for justice in the history of the United States of America," said Angelica Salas, executive director for the Coalition for Humane Immigrant Rights of Los Angeles (CHIRLA), a regional organization with national impact focused on immigrant and civil rights. "In one sweep, the Supreme Court has sided with Arizona and allowed racial profiling as an acceptable law enforcement tool."

Proponents of strict immigration enforcement praised the High Court’s support for police checks of immigration status.

“The United States Supreme Court has made it very clear that state and local governments have an important role to play in enforcing federal immigration laws,” said Dan Stein, executive director of Federation for American Immigration Reform. “Even if the Obama administration refuses to enforce most immigration laws, states have the power to deter and discourage illegal aliens from settling or remaining within their jurisdictions.”

Hispanic Leadership Network Executive Director Jennifer Korn said federal inaction on illegal immigration had forced Arizona and other states to take the matter into their own hands.

"The blame for inaction cannot be placed on either political party, but on forces within both parties,” Korn said. “It’s unfortunate and undisputable that during the first two years of this Administration, the President and a Democrat-controlled Congress had the opportunity to push through immigration reform, but chose not to. It’s disappointing that this President only talks about immigration when it is politically convenient for him.”

Perspectives on the court's mixed opinion of Arizona's law varied for the most part.

Fox News Senior Judicial Analyst Judge Andrew Napolitano said: "The heart and soul of the Arizona statute has been struck down by the Supreme Court, consistent with previous Supreme Court opinions that basically say for better or for worse whether you like it or not immigration is a federal issue to be administered by the United States of America by the federal government and not by the states.”

Napolitano continued: “Basically the court is saying to those in Arizona who are understandably unhappy with the administration of immigration law by this administration, if you don’t like it -- vote them out of office but don’t try to change the law because you are essentially without authority or sovereignty to do that.”

Staff writers Elizabeth Llorente, Roque Planas and Bryan Llenas contributed to this report.

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