The latest Syrian assault on its population and international reactions to it has once again raised the question, what does the “responsibility to protect”(R2P) mean in practice?

In the case of Libya, it meant a UN Security Resolution authorizing use of force and a NATO operation to protect civilians and civilian-populated areas under attack or threat of attack. However, after more than five months of an air campaign and maritime embargo, the limits of external military action are obvious.

In spite of that, leaders seem to be following a familiar path with Syria. UN Secretary General Ban Ki-moon called for an end to violence. The United States imposed a new round of sanctions. Russia called on the Syrian government “to stop the violence and to introduce deep political changes.” Turkey wants “the bloodshed to stop.” Even Saudi Arabia, not known for its championing of human rights, called for the Syrian leader to stop the “killing machine and end the bloodshed.”

The international reactions to the Syrian government’s violence against civilians are both a product of the brutality and a change in international thinking. In 2009, Ban outlined three key elements of R2P. First, he noted that states have the primary responsibility to protect their populations against genocide, war crimes, ethnic cleansing and crimes against humanity. Second, the international community should provide assistance to states in building capacity to protect their populations from catastrophe by addressing underlying conditions. Third, the international community should take timely action when states fail to protect their populations.

As the 2009 Report of the UN Secretary-General on R2P notes, “the strategy stresses the value of prevention, and, when it fails, of early and flexible response tailored to the specific circumstances of each case.” The key to prevention lies in identifying states at risk and developing appropriate responses to aid governments’ efforts to promote development and improve standards of living. In short, it is unacceptable to wait until civil war breaks out or masses of people become internally displaced or refugees.

When it comes to Syria and Libya, it appears the international community is too late or that the R2P doctrine is not easy to implement. Joshua Muravchik wrote in World Affairs,

R2P at best will be a flawed principle of moral action because it cannot be applied even-handedly. No matter what the regime in Beijing, for example, does to its own citizens, the use of outside military force to protect them is unimaginable. Who will invade China? Nonetheless, for this principle to deserve to be taken seriously, it should be applied as uniformly as possible. The situation in Syria is not the same as in Libya: for one thing, the Syrian people have not called for outside armed help. But if Assad goes on a mass killing spree (as his father did in the city of Hamma in 1982) and the Syrian dissidents do call for outside help, then what? It is likely that the Obama administration would shed its perverse solicitude for that regime. But it is inconceivable that the UN—i.e., Moscow and Beijing—would.

Muravchik neatly summarizes the conundrum—R2P cannot be evenly applied since some states are impervious to international intervention due to economic, political, or military constraints. Adding to this is the recognizable limits of external military intervention. As events in Libya illustrate, external actors have limited capabilities and capacity to influence the course of political events. Wanting Libya’s Gaddafi or Syria’s al-Assad removed is not the same as removing either or stopping violence against civilians.

As the international community considers what next in Libya and Syria, it must be aware of the dangers that abrupt change can bring. Removing entrenched political regimes creates winners and losers; as witnessed in many parts of the world, the winners are challenged to create peaceful national reconciliation and the international community struggles to bring stability, security, and development.

Derek S. Reveron, an Atlantic Council contributing editor, is assigned to NTM-A; he is the author of Exporting Security: International Engagement, Security Cooperation, and the Changing Face of the U.S. Military. He is currently on leave from the Naval War College.