A federal lawsuit is never a laughing matter – especially when the U.S. Department of Justice signs the complaint. But the Obama administration's complaint against Arizona faces serious obstacles in the federal courts.

The administration needs to show that S.B. 1070, Arizona's law authorizing state officials to enforce federal immigration law, is "preempted" – that it runs afoul of the Constitution's Supremacy Clause, which confirms that federal law supersedes state law.  To that end, the complaint's opening paragraphs stake an uncontroversial claim: "[i]n our constitutional system, the federal government has preeminent authority to regulate immigration matters."  

Certainly no one would dispute that the federal government is the "preeminent" architect of the nation's immigration policy.  But it is quite another thing to say that federal law, through the Constitution's Supremacy Clause, preempts S.B. 1070.  In U.S. v. Arizona, the administration will have to prove the latter point – and that will be no small task.

The administration's primary obstacle is De Canas v. Bica (1976), in which the Supreme Court emphatically declared that federal immigration laws did not prohibit the states from enforcing the policies embodied by those federal immigration laws. (In that case, the state law was a California prohibition against the employment of illegal aliens.)  The Court reviewed the text and history of the federal Immigration and Nationality Act, and found no indication that "Congress intended to preclude even harmonious state regulation touching on aliens in general, or the employment of illegal aliens in particular."  According to the Court, states may enforce laws consistent with federal immigration laws, so long as the state does not "impose additional burdens not contemplated by Congress."

Arizona drafted its laws with De Canas firmly in mind, as S.B. 1070's architect, law professor Kris Kobach, explained in a recent interview. In fact, Arizona's recent brief in a separate lawsuit makes this very point. Last month, Arizona moved to dismiss Friendly House v. Whiting, a class action lawsuit brought against S.B. 1070 by the ACLU and other groups. Responding in its motion to dismiss the lawsuit that was based on arguments that S.B. 1070 improperly regulates immigration, Arizona drew De Canas's crucial distinction: The ACLU is "confusing enforcement of federal immigration regulations (which S.B. 1070 seeks to accomplish) with enactment of Arizona-specific 'regulation of immigration' (which federal law would preempt)."

Arizona's brief lays out in straightforward detail the absence of any of the traditional bases for federal preemption of state law. As De Canas explained, the federal immigration statutes lack an express statement that federal law prohibits states from enforcing federal immigration law. Similarly, federal law does not so thoroughly "occupy the field" of immigration regulation that it leaves no room for state involvement in the federal statutes' enforcement.  Finally, S.B. 1070 does not "conflict" with federal law: It neither interferes with the accomplishment of federal immigration statutes nor creates legal standards that contradict the federal statutes.

While the Obama administration phrased its complaint in broad terms, it appears to be framing this case primarily as one of "conflict" or "field" preemption. Namely, in administering the federal immigration laws, "the federal agencies balance the complex – and often competing – objectives that animate federal immigration law and policy," and that the "nation's immigration laws reflect a careful and considered balance of national law enforcement, foreign relations, and humanitarian interests."  In fact, the Obama administration goes so far as to assert that S.B. 1070 prevents it from getting tough on truly nasty illegal immigrants: "S.B. 1070 disrupts federal enforcement priorities and resources that focus on aliens who pose a threat to national security or public safety ... undermin[ing] the federal government's careful balance of immigration enforcement policies and objectives."

But that line of argument wholly misses the point.  When courts decide whether federal law preempts state law, the question is not whether the state law conflicts with the president's selective enforcement of federal statutes.  The question is whether the state law "stands as an obstacle to the accomplishment ... of the full purposes and objectives of Congress," as embodied by the federal statutes.  S.B. 1070 satisfies that test – it does nothing more than allow state officials to enforce Congress's purposes and objectives as expressed in current federal statutes.

And while the Obama administration's complaint cites several federal statutes that stop short of levying upon illegal immigrants the sorts of criminal sanctions imposed by S.B. 1070 (e.g., humanitarian exceptions of asylum), it identifies no part of S.B. 1070 that specifically requires state officials or judges from incorporating those federal limits into their own actions, to the necessary extent. Indeed, by suggesting that S.B. 1070's sanctions against persons "unlawfully present" in the United States do not take into account federal asylum determinations, the Obama administration interprets S.B. 1070 in the worst possible light.  But a cardinal rule of statutory interpretation is that courts should, whenever possible, interpret statutes in a way that minimizes or avoids such constitutional conflicts.

As it happens, the Supreme Court may weigh in on these types of questions long before the lower federal courts resolve the Obama administration's case.  In the upcoming term, the Court will hear Chamber of Commerce v. Candelaria, which presents a similar constitutional challenge to another Arizona immigration-related statute – one that was signed into law, ironically enough, by then-Governor Janet Napolitano.  In that case, the traditionally liberal Ninth Circuit ruled in Arizona's favor, holding that federal law does not preempt Arizona's law punishing employers that hire illegal aliens.

No one gets rich betting big against the U.S Department of Justice.  Its lawyers are among this nation's very finest.  But the Obama administration's decision to commence this controversial lawsuit will require them to put their formidable talents to the test.

Adam J. White is a lawyer in Washington, D.C.