Interventionists are cheering the United Nations for authorizing a no-fly zone over Libya. The U.N.’s imprimatur, they say, is necessary for U.S. participation, which is essential for the mission’s success. But Mr. Obama’s war on Libya is a mess because he gave the United Nations the role of the decider.

A week into the mission, the purpose of Operation Odyssey Dawn is unclear. Coalition partners don’t know who is in charge. They can’t agree on the objective. Some say the operation will take a matter of days, others predict decades. Some leaders believe Muammar Gaddafi should be killed, others say jailed, others still would allow him stay in power if he promises to behave himself. There is bickering and backstabbing in the NATO coalition. On Capitol Hill, some members of Congress are talking about impeaching the president.

This is the art of war as practiced by the international community.

Americans should have deep concern about Obama’s Libyan escapade, its consequences, and the decision process that led to U.S. involvement.

A case can be made for putting Gaddafi out to pasture. He’s a murderer responsible for the deaths of hundreds of Americans. The 1988/1989 bombings of Pan Am flight 103 and UTA flight 772 — orchestrated by Libyan terrorists — took the lives of nearly 200 Americans including the wife of a U.S. ambassador. His 1986 attack on the La Belle Nightclub in West Berlin left two U.S. soldiers dead and 79 other Americans wounded.

Since these atrocities, however, Gaddafi was brought in from the cold. After the U.S. intervention in Iraq, the Libyan loon happily handed over his weapons of mass destruction. He made nice-nice on the world stage for a few years and in 2006 the Bush administration restored diplomatic relations between the United States and Libya.

More recently, as the Arab uprising appeared on the streets of Tripoli, Gaddafi violently declined invitations to step down. Libyan protestors were the victims of his brutality. So the United Nations, citing a recently-approved theory called the “Responsibility to Protect,” called on the United States to intervene and Obama obeyed.

Now, significant U.S. assets — carriers, subs, fighter jets and surveillance aircraft — have been obligated to a civil war on the African continent. Billions of dollars that we don’t have are being spent on behalf of an opposition we don’t know or understand. Most important, the lives of American service members have been put in harm’s way.

This was all done without a peep from the United States Congress.

House Speaker John Boehner groused that Mr. Obama “has a responsibility to define for the American people, the Congress, and our troops what the mission in Libya is . . . and make clear how it will be accomplished.” If Boehner and his committee chairmen want to know what our troops are doing in Libya, they should consult the United Nations — they know all about it. It was the U.N. that “authorized” the mission and put the plan together. It was the United Nations that Mr. Obama turned to for permission.

Obama commenced America’s third war in the Middle East, without ever consulting the Congress — a scenario he decried as a U.S. senator and candidate for president. In this instance, he gave his allegiance to the Charter of the U.N. and turned his back on the Constitution.

Secretary of State Hillary Clinton did the same — giving the Bronx cheer to her former colleagues in the Senate, saying, “We think it’s important that the United Nations make this decision, not the United States.” Joint Chiefs chairman Admiral Mike Mullen explained it this way: “We’re very focused on the limited objectives that the president has given us and actually the international coalition has given us.”

And what is it that we are fighting for in Libya? The president explained that without the U.S. military’s involvement, “the words of the international community would be rendered hollow.” Translation: we’re fighting for the credibility of the United Nations. Obama felt like going in to Libya and he cherry-picked his authority for doing so as the U.N.

If Congress allows Mr. Obama to bypass them on the most important decision facing a nation – going to war — then he will have no reason to stop unilaterally nationalizing industry, socializing medicine, racking up trillions of dollars in debt, and ignoring the will of the people.

Thomas P. Kilgannon is the President of Freedom Alliance and the author of Diplomatic Divorce: Why America Should End Its Love Affair With the United Nations.