This afternoon, President Obama will convene a conference call for members of Congress on the operation in Libya, a tacit acknowledgment that there is great concern about the strategy and the constitutional legitimacy of the mission. Press Secretary Jay Carney said at his briefing that the President “update them on the transition of command and control to NATO.”

This comes as members of Congress, even ones not usually inclined to criticize a President of their own party on foreign policy questions, have become more outspoken about the mission in Libya. Jay Rockefeller, the chairman of the Senate Intelligence Committee, had this to say:

“I know the president carefully weighed all the options before taking this emergency action, but now that our military has prevented an immediate disaster, I have very serious concerns about what this intervention means for our country in the coming weeks,” Sen. Jay Rockefeller (D-W.Va.) said in a statement. “Our military, and our budget, are stretched thin fighting two wars already, and I want to avoid getting into another conflict with unknown costs and consequences.

“I feel very strongly that we need to avoid deep military involvement in a third foreign country — particularly in a country whose politics and society are largely unknown to us.”

Rockefeller and others in Congress have been somewhat mollified by the transition of command to NATO. But there’s still the lingering question of the constitutionality of the military action in the first place. Yale Law Professor Bruce Ackerman bluntly called the war unconstitutional in a post today.

In taking the country into a war with Libya, Barack Obama’s administration is breaking new ground in its construction of an imperial presidency — an executive who increasingly acts independently of Congress at home and abroad. Obtaining a U.N. Security Council resolution has legitimated U.S. bombing raids under international law. But the U.N. Charter is not a substitute for the U.S. Constitution, which gives Congress, not the president, the power “to declare war.”

After the Vietnam War, Congress passed the War Powers Resolution, which granted the president the power to act unilaterally for 60 days in response to a “national emergency created by attack upon the United States, its territories or possessions, or its armed forces.” The law gave the chief executive an additional 30 days to disengage if he failed to gain congressional assent during the interim.

But, again, these provisions have little to do with the constitutionality of the Libyan intervention, since Libya did not attack our “armed forces.” The president failed to mention this fundamental point in giving Congress notice of his decision on Monday, in compliance with another provision of the resolution. Without an armed “attack,” there is no compelling reason for the president to cut Congress out of a crucial decision on war and peace.

If the President asked for authorization, he probably would have gotten it, at least in the Senate. I would argue that Congress isn’t necessarily gung-ho about having the responsibility, and are generally happy to hand that over to the executive. But that fact, and the past performance of other chief executives ignoring Congress on war powers, does not magically make this action constitutional. After all, even George W. Bush asked for authorization for his wars.

Sadly, I think Congress has many other things on their minds other than reining in the imperial Presidency.

UPDATE: The White House gives a readout of the briefing.