WASHINGTON Though overshadowed by the shocking Supreme Court decision on health care, the court’s Arizona immigration decision, issued three days earlier, remains far more significant than appreciated. It was generally viewed as mixed or ambiguous because the Justice Department succeeded in striking down three of the law’s provisions. However, regarding the law’s central and most controversial element – requiring officers to inquire into the immigration status of anyone picked up for some other violation – the ruling was definitive, indeed unanimous.

No liberal-conservative divide here. Not a single justice found merit in the administration’s claim that this “show me your papers” provision constituted an impermissible pre-emption of federal authority.

On what grounds unconstitutional? Presumably because state officials would be asking about the immigration status of all, rather than adhering to the federal enforcement priorities regarding which illegal aliens would not be subject to deportation.

For example, under the Obama administration’s newly promulgated regulations, there’ll be no more deportation of young people brought here illegally as children (and meeting certain chronological criteria). Presumably, therefore, the Arizona law is invalid because an officer might be looking into the status of a young person the feds now classify as here legally.

Beyond being logically ridiculous this argument is “an astounding assertion of federal executive power,” wrote Justice Samuel Alito in a concurrence. The Obama Justice Department is suggesting that “a state law may be pre-empted, not because it conflicts with a federal statute or regulation, but because it is inconsistent with a federal agency’s current enforcement priorities.”

And there’s the rub: the Obama administration’s inability to distinguish policy from law. This becomes particularly perverse regarding immigration when, as Justice Antonin Scalia points out, what the administration delicately calls its priorities is quite simply a determination not to enforce the law as passed.

Consider this breathtaking cascade: An administration violates its constitutional duty to execute the law by deliberately refusing to enforce it. It then characterizes its non-enforcement as simply establishing priorities. It then tries to strike down a state law on immigration on the grounds that it contradicts federal law – by actually trying to enforce it!

The logic is circular, oxymoronic and the very definition of executive overreach. During the Bush-43 years, we were repeatedly treated to garment-rending about the imperial presidency, to major hyperventilation about the “unitary executive.” Yet the current administration’s imperiousness has earned little comparable attention.

Perhaps because President Obama has been so ineffective. It’s hard to call someone imperial who’s failed so consistently.

Regardless of results, however, Obama’s presumption is Olympian. He takes America into a war in Libya with U.N. approval, but none from Congress. Yet that awful Bush had the constitutional decency to twice seek and gain congressional approval before he initiated hostilities.

The Department of Health and Human Services issues Obamacare regulations treading so heavily on the free-exercise rights of Catholic institutions that Obama’s own allies rebel. The new regulation concocted to tame the firestorm blithely orders private insurers to provide free contraceptives to employees of the objecting religious institutions. By what possible authority does a president order private companies to provide free services?

And now immigration. Obama adopts a policy of major non-enforcement of the immigration law – a variant of the very DREAM Act he could not get through even a Democratic Congress – and promulgates it unilaterally, while his Justice Department claims the right to invalidate state laws that might in some way impinge on that very non-enforcement.

The Republican presidential campaign centers on the ineffectiveness of this administration: failure at home, passivity abroad. A fine electoral strategy. But as citizens we should be grateful. Given the administration’s extravagant ambitions, incompetence is its saving grace.