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 unanimous.

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.

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.

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.

This is what makes so egregious the Obama claim that Arizona is impermissibly undermining federal law.

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!

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. Or maybe not. You can surely be imperial and unsuccessful. Waterloo comes to mind.

• Obama 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.

• And now immigration. 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.

Charles Krauthammer is a columnist for The Washington Post and a regular panelist on PBS and Fox News. He can be contacted at:

letters@charleskrauthammer.com