“There is only one justification for military intervention [in Libya]: protecting people being murdered by Gadhafi.” So says Gareth Evans, father of the “responsibility to protect” doctrine that some say is behind President Obama’s decision to intervene in Libya.

This idea turns U.S. national security policy on its head. Instead of using military force to protect Americans or defend our interests, we would be obligated to use force to protect people in other countries, when so directed by the U.N. Security Council.

Where does this idea come from? Not surprisingly, from the U.N.

The 1990s genocides in Srebrenica and Rwanda sparked U.N. debate on how to prevent such massacres. This led to a 2001 U.N.-commissioned study, “The Responsibility to Protect: Report of the International Commission on Intervention and State Sovereignty.” That report laid out the doctrine’s main ideas: All nations have a responsibility to protect their citizens from large-scale loss of life or ethnic cleansing, and if a nation failed to do this, the “international community” — working through the U.N. — had a “responsibility” to protect the aggrieved population.

The U.N. General Assembly enshrined this idea in the 2005 Millennium Summit Outcome Document. The U.S. accepted, but stipulated that the document did not “obligate” nations to intervene. The Security Council subsequently reaffirmed the “responsibility” lines on several occasions, most recently in this year’s first Libyan resolution. It referenced the “authorities’” responsibility to protect its population.

There are many problems with this idea. First is the hypocrisy of protecting one population while ignoring others. Why intervene with force to stop a potential massacre in Libya and ignore real genocide in Sudan’s Darfur region? Why were some of the same people who advocate a responsibility to protect in Libya so fiercely opposed to intervening in Iraq, where Saddam Hussein killed about 300,000 civilians?

Given its scattershot application, “responsibility to protect” fails as a principle. But it comes in handy for those seeking to justify the pursuit of objectives seldom admitted outside the halls of the United Nations.

What are these objectives?

First, to undermine the idea that force should be used only to protect national security. Advocates argue that protecting civilians is the only “just cause” for using force. Defending our allies from attack or even launching military interventions overseas to take out terrorist bases would, under this definition, be “illegitimate.”

The second objective is to elevate the Security Council as the only body that can legitimately authorize the use of force by any nation, including the U.S. This has obvious implications for the U.S. Constitution, which recognizes the war-making powers only of the President and the Congress.

Our nation has the bulk of the world’s military forces. This doctrine would constrain us from using force for our own protection (except for very obvious invasions). Worse, it leaves our forces on the hook to intervene overseas at the behest of the Security Council, at our expense. It relegates our military to the status of U.N.-mandated world police force.

This makes no sense in terms of U.S. national security or in terms of the U.N. Charter. Article 51 of the Charter affirms that nations can use military force for self-defense. The Charter also says that when force is used for other purposes, it must do so to counter “international” threats and restore “international” peace. And it says “nothing contained in the present Charter shall authorize the United Nations to intervene in matters which are essentially within the domestic jurisdiction of any state.” In other words, internal abuses by states are no excuse to intervene.

Advocates of the responsibility to protect may find this provision inconvenient, heartless or even “illegitimate.” But that’s what the Charter says. As envisioned by many of its supporters, this doctrine violates the U.N. Charter.

The Security Council has pecked away at national sovereignty for years, justifying arms embargoes, no-fly zones and sanctions.

But it has recently become far more willing to ignore this Charter restriction in response to perceived threats to civilian security. Before dismissing the “slippery slope” argument that the Security Council will someday claim exclusive jurisdiction over the use of force, remember how far we have drifted away from the original purposes of the U.N. Charter.

“Responsibility to protect” is pure sophistry, riddled with contradictions. In reality, it is a cynical attempt to assert external decision-making powers over the use of U.S. military force. By trying to change the rules, advocates hope to delegitimize America’s traditional use of force to defend itself and its allies and to put that decision in the hands of an international body that includes France, Russia and China.

It’s easy to see why Russia and China would want the U.N. to control U.S. decisions to use military force. It’s not at all clear why a U.S. president would want that.

Kim R. Holmes, a former assistant secretary of state, is a vice president at the Heritage Foundation