"For each state, and each locality, to set its own immigration policy in that fashion would wholly subvert Congress's goal: a single, national approach," he says.
Arizona's SB 1070 is best known for a provision that requires state and local law enforcement officials to check the immigration status of anyone detained in a traffic or other stop whenever authorities have reason to suspect the individual is in the United States illegally.
In addition, the state law also requires noncitizens and nonpermanent residents in Arizona to carry an immigrant registration document like a green card. It makes it illegal for an undocumented immigrant to work or apply for work in Arizona, and it empowers the police to make warrantless arrests when the officer has probable cause to believe the subject has committed a deportable offense.
Critics say the law will lead to illegal racial profiling. Supporters say it is an effort to make up for lax immigration and border enforcement by the administration.
In 2010, the Obama administration sued Arizona to block the law. A federal judge issued an injunction. A panel of the Ninth US Circuit Court of Appeals affirmed.
Arizona appealed to the Supreme Court.
In addition to the legal issues, the case is a potential political blockbuster in a presidential election year.
The president's kinder, gentler immigration approach is believed to have paid significant political dividends to the president and the Democratic Party among Latinos.
Republicans are split on how best to address immigration. Some favor the tough approach embraced by Arizona, while others are concerned that it could drive Latino voters wholesale to the Democrats.