The Obama administration will sue Arizona for trying to help Washington enforce federal immigration laws, but flatly rejects the notion of suing sanctuary cities that blatantly defy those same laws. That announcement two weeks ago revealed the hypocrisy and utter contempt for the rule of law rampant in Eric Holder’s Justice Department.

It was the latest example of the Department letting partisan politics, rather than the interests of justice and the impartial enforcement of the law, drive its legal decisions. In this instance, it both threatens national security and undermines public confidence in our legal system.

The very weakness of the Department’s legal arguments in the Arizona suit betrays its political genesis. As the brief filed on behalf of Arizona by nine other states persuasively argues, Arizona is not interfering with federal authority: it has neither created new categories of aliens nor attempted to independently determine the immigration status of aliens. Arizona’s law simply requires local law enforcement officers to check the immigration status of individuals arrested for other reasons. This is exactly the regulatory scheme of concurrent enforcement envisioned by federal immigration law.

The Justice Department’s suit directly contradicts the 2005 Supreme Court decision in Muehler v. Mena. In that case, all nine justices upheld the right of local police officers to question a detained individual’s immigration status while a search warrant was being executed. The suit also flies in the face of Estrada v. Rhode Island, in which the First Circuit Court of Appeals this February upheld a state trooper’s questioning of immigration status during a traffic stop. This is the exact policy being implemented in Arizona.

Federal courts have long upheld the power of state law enforcement officers to arrest those who violate federal law, as long as it is also a violation of state law, including immigration laws. The inherent authority of local police to arrest immigration violators was outlined in 2002 in a legal memorandum issued by the Department of Justice’s Office of Legal Counsel. Yet Attorney General Holder has filed a lawsuit making claims completely at odds with an opinion issued by his own department.

Holder’s suit also conflicts directly with federal immigration law. The Illegal Immigration Reform and Immigrant Responsibility Act of 1996 (8 U.S.C. §1373) specifically mandates that no federal, state, or local government can “prohibit, or in any way restrict, any government entity or official from sending to, or receiving from, the Immigration and Naturalization Service [now Immigration and Customs Enforcement or ICE], information regarding the citizenship or immigration status, lawful or unlawful, of any individual,” a provision upheld by the Second Circuit Court of Appeals in 1999. Congress wanted local governments to get information on immigration status from the federal government – and that is exactly what the Arizona law requires for anyone arrested in the state. Yet Holder is trying to prevent Arizona officials from checking “the citizenship or immigration status” of “any individual.”

Now we’re awaiting a ruling by a federal judge on the Justice Department’s request for a temporary injunction to stop the law from going into effect on Thursday. It’s clear, though, that the only way that judge could possibly rule in the Department’s favor is by ignoring the law and this precedent.

Justice Department spokesman Tracy Schmaler asserts that Arizona is “actively” interfering with federal law while sanctuary cities are just not using their resources to enforce federal law. This bogus claim displays fundamental ignorance of these federal legal requirements. Rep. Lamar Smith of Texas, the ranking Republican on the House Judiciary committee and the chief author of the 1996 immigration law, rightly calls it “absurd.” Cities like San Francisco not only do not enforce federal immigration laws, some violate it by protecting aliens from deportation and refusing to cooperate with or provide information to immigration officials.

As the nine states note in their brief, the Justice Department is trying to negate the “preexisting power of the States to verify a person’s immigration status and similarly seeks to reject the assistance that the States can lawfully provide to the Federal government.” Holder’s claim that Arizona is interfering with federal power to regulate immigration is near frivolous.

Arizona simply requires that law enforcement personnel (1) ascertain the immigration status of people they have lawfully detained for some other reason and (2) report to the federal government the presence of any detainee determined to be here illegally. If the Obama administration wants to ignore that information and reject that assistance, it has that option. The only possible “interference” with federal power is the risk that the feds might be publicly embarrassed by a policy of non-enforcement. Apparently the White House and DOJ consider embarrassment a federal offense.

Holder makes one further -- yet equally absurd -- claim: that by trying to deter the movement of illegal aliens into Arizona, the state is restricting interstate commerce and thus violates the Commerce Clause. How can deterring the entry of people who have no legal right to enter possibly violate interstate commerce? It is the same as saying that -- notwithstanding federal laws that bar importation of heroin -- a state that busts heroin traffickers is flouting the Commerce Clause.

Federal law stipulates that any person who “conceals, harbors, or shields from detection, or attempts to conceal, harbor, or shield from detection,” an illegal alien is committing a crime. It is also criminal just to “encourage” residence by illegal aliens. Yet sanctuary cities like San Francisco have enacted formal policies that embrace all these illegal acts. Such policies lead directly to further crimes, such as the vicious murder of a father and his two sons on a San Francisco street. The killer was an illegal alien with two prior felony convictions -- yet on neither occasion did San Francisco authorities notify the feds of his presence. Had they done so, he would not have been able to gun down Tony Bologna, 48, and his sons Michael, 20, and Matthew, 16, as they sat in their car on June 16, 2008.

Holder’s refusal to sue sanctuary cities is an abrogation of his responsibility as the nation’s chief federal law enforcement officer. Unlike Arizona, many of these cities have policies that violate federal law.

The Obama administration claims Arizona’s law will “disrupt federal immigration enforcement.” But the only thing it could possibly disrupt is federal non-enforcement. As the elections approach, Holder’s suit may help gin up enthusiasm among the president’s more radical political allies, such as La Raza. But using the law enforcement powers of the federal government to achieve political ends is a dangerous abuse of power.