The recent unilateral U.S. military strike on Syria has brought mixed reactions from the international community. While most of its allies and partners gave their support to the U.S., Russia labeled the military action as an aggression against international law. Even among those countries backing the U.S., it is interesting to note that many justified their support on moral and political grounds. These countries unanimously kept an official silence on the legality of the U.S.’ use of force against Syria.
A US cruise missile being fired at al-Shayrat airbase. (US Department of Defense)
Several questions remain to be answered. First, what is the exact legal basis for the U.S. military action under international law? Second, if there is no legal basis under international law, could moral justifications or any other justifications be invoked by states to justify their use of force against other states? And finally, in light of the controversy over who was behind the chemical weapons attack, can the U.S. rely on itself to make judgments and moral justifications for use of military force against a sovereign state?
Before answering those questions, it is necessary first to review what are the rules of international law on the use of force by states. Not withstanding the early development of international law on the use of force, the greatest contribution made by the UN Charter to the development of international law on the use of force is the basic principle of prohibiting it in international relations, contained in Article 2(4). This provides that ‘All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the purposes of the United Nations’. This general prohibition admits of two exceptions: the use of force by states in individual or collective self-defense, based on Article 51 of the UN Charter, and the use of force as part of collective enforcement measures authorized by the UN Security Council, based on Article 42 of the UN Charter. Those rules on the use of force for self-defense and under UN Security Council mandate constitute the Collective Security System (CSS) based on the UN Charter.
It is hard for the U.S. to make either arguments. There is no authorization from the UN Security Council in this regard. Nor could the U.S. military strike be easily justified as self-defense of the United States as the U.S. is by no means subject to armed attacks from Syria.
As for the moral reasons for use of force, international law is quite value-free in this respect. Needless to say, the moral justification in response to the use of chemical weapons by Syria government relied solely on the U.S. intelligence resources, which have proved to be less credible since the 2003 U.S. invasion of Iraq. At a minimum, the judgment on who was behind the use of chemical weapons against civilians should be based on law and facts and upon UN- authorized investigations.
It has to be noted that, in its official statement, the U.S. is clever enough to emphasize its compliance with the law of armed conflict and intentionally mix together the application of rules of both Jus ad Bellum (rules of international law on the right to resort to force) and Jus in Bello (rules of international law governing the conduct of operations), which are in fact two separate systems in international law. In particular, the claimed compliance with the rules of Jus in Bello by the one state does not in any way justify its violation of rules of Jus at Bellum. The same goes with the scenario that one state could not justify its use of force against another state under the rules of Jus at Bellum just because the other state violated the rules of Jus in Bello. In this regard, even if Syria is found committing war crimes by violating rules of International Humanitarian Law to use chemical weapons against civilians, this does not give legal justification for the U.S. to use force against Syria.
The above being said, other justifications that could possibly be invoked by the U.S. and its supporters may include “humanitarian intervention” or the institution of “the Responsibility to Protect (R2P)”. "Humanitarian intervention", which remains a very controversial concept in international law, involves situations where a state uses violence against its own population and consequently other states may intervene to protect the population from its own state and government. Although the NATO air strikes in 1999 against Serbia in the Kosovo conflict have been hailed by many as a successful example of humanitarian intervention practice, this justification was then rejected by the overwhelming majority of nations. It could be said that there is no consensus regarding the right to use force in international law to conduct humanitarian intervention and unilateral humanitarian intervention without UN Security Council authorization. The same is valid for the so-called institution of the responsibility to protect. The R2P does not provide any new legal basis for using force under Jus at Bellum and the use of force under the doctrine of R2P must be for collective purpose and under the UN Security Council mandate.
International law on the use of force has evolved and developed as the basic rules of any society. To save succeeding generations from the scourge of war, the UN Charter laid as its fundamental principle the prohibition on threat or use of force in international relations and envisaged the Collective Security System as an implementation mechanism. At the center of this CSS is a monopoly control of use of force by the UN Security Council, leaving aside the exceptional case of self-defense.
However, history shows that this UN-Charter based system is constantly threatened by the unilateral use of force by major powers. The worst case of such unilateralism has been the 2003 Iraq war, which took tolls on both sides of the armed conflict and has long-lasting consequences far beyond the end of the war. The 2003 Iraq war claimed the lives of 179 British soldiers, thousands of American soldiers, and hundreds of thousands of Iraqi civilians, exacerbating the country’s faction divisions and causing endless unrest. Worse, the so-called weapons of mass destruction were never found in Iraq. The war also failed to "remold" Iraq as an exemplary democracy in the Middle East, as tensions between disputing forces remain high and the political vacuum has given rise to terrorist groups like the Islamic State. Moreover, the ouster of the Saddam Hussein government, which left more than 1 million Iraqis (mainly civilians) homeless, could be seen as a major cause of the ongoing refugee crisis in Europe.
The tragic consequences of the 2003 Iraq war has sparked huge debate in international law and helped to bring international community, in particular western states, back from unilateralism to multilateralism. An inquiry was conducted in the United Kingdom to look at its role in the 2003 US-led invasion of Iraq on the basis of flawed intelligence, culminating in the critical Chilcot report. The Obama administration was seen as abandoning unilateralism and relying more on multilateralism compared with the previous administration.
However, history repeats itself. The apparent unilateral use of force in violation of international law by the U.S. sends an alarming signal to the international community. International attention has focused on whether this is just a one-off deal or it signals the Trump administration’s change of policy back to unilateralism. The latter would make unpredictable consequences to international peace and stability an ongoing problem.
