Why the Justice Department Lawsuit Against Arizona Will Likely Fail

The federal government has just filed suit challenging the state of Arizona’s new anti-illegal immigration law. The basis? The Supremacy Clause, which says that federal law trumps state law.

But that argument should fail in a court of law because the Arizona law mimics the federal law. It basically gives the state a mechanism to enforce federal law, to turn over people police have a reasonable suspicion to believe may be illegal over to the feds.

The Supremacy Clause only comes into play when a state law is “contrary” to a federal law or the Constitution. And courts have ruled that the states have “concurrent authority” when state law only mimics federal law. -- Five federal appeals courts have applied this in context of illegal aliens, upholding states’ rights to arrest illegals.

It is also being reported that the other ground for the legal challenge is racial profiling but the Arizona law specifically prohibits that. It states that the police officers must have a "legal" reason for stopping a person before questioning.

Finally, a 2002 memo from the Department of Justice concluded that state police have “inherent power” to arrest undocumented immigrant for violating federal law. That memo will come back to haunt them now.

Lis Wiehl is a Fox News legal analyst and former federal prosecutor.

Fox Forum is on Twitter. Follow us @fxnopinion.