The escalating death toll in Syria, which exceeds 60,000, has increased pressure on President Barack Obama to do more to help the Syrian opposition. But traditional legal rules that protect international peace and security constrain the president’s options. Although the administration recognized the Syrian Opposition Council last month as the “legitimate representative of the Syrian people,” that announcement created no new legal basis for Washington to give weapons to Syrian rebels or to intervene with military force against the Assad government. If Bashar Assad’s atrocities continue, Obama will find it difficult to provide more U.S. assistance consistent with international law.

The U.N. Charter prohibits member states from using force against or intervening in the internal affairs of other states unless authorized by the U.N. Security Council or justified by self-defense. These rules make it unlawful for any country to use direct military force against the Assad regime, including establishing “no-fly zones” or providing arms to the Syrian opposition without Security Council approval. Russia and China, of course, have continued to block such approval.

Over the years, people in and outside government advocating U.S. intervention — whether in Syria, Libya or other circumstances — have chafed at these restrictions. Many human rights advocates believe that traditional non-intervention principles unduly constrain efforts to prevent mass atrocities; some have urged recognition of a new international norm that would allow “humanitarian intervention” in such cases. But most countries, including the United States, have resisted a doctrine of humanitarian intervention because it is likely to be abused by potential aggressors.

Many conservatives have long been skeptical of international legal rules that purport to restrict sovereign nation-states’ freedom of action. In an unusual convergence, these conservatives agree with liberal human rights advocates that international law should not prevent the use of force or other forms of intervention to help the Syrian opposition.

In the president’s own words, his endorsement of the Syrian Opposition Council on Dec. 11 was a “big step.” His announcement followed similar endorsements by Britain, France, Turkey, the European Union and the seven-country Gulf Cooperation Council and paved the way for increased U.S. humanitarian aid to the opposition. Such aid reached more than $210 million last month.

But Obama stopped short of recognizing the opposition as the “government” of Syria. The United States continues to maintain diplomatic relations with Damascus and to treat the Assad regime as Syria’s government.

In July 2011, by contrast, the administration recognized the Libyan opposition as the “legitimate governing authority in Libya.” That represented an unusual departure from past U.S. diplomatic practice of recognizing “states” but not “governments,” especially in the face of competing claims. Recognizing the Libyan opposition as that country’s government allowed the Obama administration to unfreeze substantial Libyan-government assets in the United States and to turn them over to the opposition.

Treating the Syrian group as the “representative” of the people does not have a similar legal effect and does not allow the United States to treat the opposition’s requests for aid or support as a legal basis for U.S. military intervention.