Wherever it has benefited trial lawyers, the Obama administration has fought against federal pre-emption of state laws. His administration, at the behest of the American Association for Justice, even issued an executive order banning new preemptive regulations, which often prevent state-level lawsuits against companies whose products adhere to federal regulations.

Now this same doctrine of preemption has become the basis for President Obama’s lawsuit against Arizona.

In this action, the United States seeks to declare invalid and preliminarily and permanently enjoin the enforcement of S.B. 1070, as amended and enacted by the State of Arizona, because S.B. 1070 is preempted by federal law and therefore violates the Supremacy Clause of the United States Constitution.

That’s only the first odd angle. Here’s another: When is the last time you saw the federal government argue that a state errs by requiring its agencies and municipalities, in one way or another, not to interfere with the enforcement of federal law?

If you haven’t seen such a thing before, it’s on page 2 of the complaint, which part of SB 1070 intended to prevent “sanctuary city” policies:

The mandate to enforce S.B. 1070 to the fullest extent possible is reinforced by a provision allowing for any legal resident of Arizona to collect money damages by showing that “any official or agency . . . [has] adopt[ed] or implement[ed] a policy” that “limits or restricts the enforcement of federal immigration laws . . . to less than the full extent permitted by federal law.”