After months of harsh rhetoric and threats, there was no surprise when the Obama administration filed a lawsuit last week in a Phoenix federal court, challenging Arizona's illegal immigration law on grounds that it violates the supremacy clause of the Constitution.
"Preemption was the only reason the federal government would be involved," said Andy Hessick, law professor at Arizona State University's Sandra Day O'Connor College of Law. "Whenever federal law conflicts with state law, federal law prevails."
The federal challenge hinges upon the fundamental if arcane legal precedent of preemption as established in Article VI of the Constitution. That clause reads: "This Constitution, and the Laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the Authority of the United States, shall be the supreme Law of the Land; and the Judges in every State shall be bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding."
"It's very fundamental, and fundamental issues sometimes escape our understanding," said Toni M. Massaro, a professor of constitutional law at the University of Arizona's James E. Rogers College of Law.
What the administration argues is that Arizona's law treads on law enforcement ground reserved for the federal government. In effect, what the Department of Justice lawyers have said is that federal statutes preempt any state efforts to enforce immigration law.
Massaro said the federal government had little choice but to file a claim against Arizona.
"If the government doesn't indicate it disagrees with Arizona in some form, it makes it harder to protect its turf," Massaro said.
While federal and state laws can and do exist in the same sphere, as in the realm of health care regulation for example, it's open for legal interpretation whether immigration is such an area of shared responsibility.
In such instances, the courts determine whether the Congress wrote a law with "pre-emptive intent," called "express preemption," or whether the intent was implied.
Express preemption generally means Congress wrote a law that explicitly gave enforcement authority to federal agencies.
"The problem is very often the Congress doesn't say explicitly if they want to allow state laws to complement federal law," Hessick said. "The courts have to guess whether Congress wanted that to happen."
The language of SB 1070 makes clear the state's intention to work in collaboration with federal law.
"This act shall be implemented in a manner consistent with federal 42 laws, regulating immigration, protecting the civil rights of all persons, and 43, respecting the privileges and immunities of United States citizens," the bill reads.
In its complaint against the state of Arizona, the federal government may be hopeful for a judicial interpretation that recognizes the pre-emptive intent of the country's immigration laws.
"Congress has exercised its authority to make laws governing immigration and the status of aliens within the United States by enacting the various provisions of the INA (Immigration and Nationality Act) and other laws regulating immigration," the claim reads.
If "implied preemption" is found, two standards exist: conflict or field preemption.
"Conflict preemption" arises when federal and state laws are written in such ways that it would be impossible to comply with both.
In the case of the Arizona law, the more likely scenario would be "field preemption," with the courts determining whether federal law occupies the entire field of immigration law.
"It's like a zone where the state is precluded from entering," Massaro said.
Complicating the issue is the government's own recognition that state and local governments can and often do partner with federal authorities in immigration enforcement.
"The federal government, moreover, welcomes cooperative efforts by states and localities to aid in the enforcement of the nation's immigration laws," according to the Justice Department claim.
Police and sheriffs departments throughout Arizona have entered into partnerships with federal immigration enforcement agencies. In addition, police across the country daily arrest suspected illegal immigrants whom federal authorities later pick up and deport.
But the federal government doesn't want Arizona or any other state enacting laws that thwart the national government's foreign policy objectives.
"If allowed to go into effect," the claim reads, "S.B. 1070's mandatory enforcement scheme will conflict with and undermine the federal government's careful balance of immigration enforcement priorities and objectives."
Proponents of Arizona's law have said that's exactly what they intend to do — complement federal immigration laws with state enforcement efforts.
The Justice Department writes that not only is immigration enforcement a federal responsibility, but that the government reserves the right not to enforce such laws.
"That's part of the argument the government has made — that non-enforcement is part of its policy," Massaro said.
The outcome of the case could have lasting impact not only on immigration law, but also toward clarifying an often-muddy area of legal interpretation.
"There are a couple of states considering laws just like Arizona's," said Carissa Byrne Hessick, law professor at Arizona State University's Sandra Day O'Connor College of Law. Byrne Hessick and Andy Hessick are married and both teach at the college.
Byrne Hessick said the federal challenge, if successful, would likely influence the decisions of other state legislatures that might try for their own immigration enforcement measures.
Another immigration-related case involving Arizona could play into the outcome of the SB 1070 saga as well. The Supreme Court recently agreed to hear arguments in the dispute over E-verify, the state's attempt to punish employers who hire illegal immigrants.
"That might prove to be a good test case," Byrne Hessick said.
The Justice Department has requested the court issue a temporary injunction to block the implementation of the Arizona law, which would go into effect July 29. No decision has been made on the injunction request.