Foreign Relations & International Law

How Does the Syria Situation Stack up to the“Factors” that Justified Intervention in Kosovo?

Ashley Deeks
Friday, April 7, 2017, 8:28 AM

As the Lawfare readership knows, the United States and its NATO allies relied on a series of factors in 1999 to argue that NATO’s intervention in Kosovo was legitimate. They used these factors to justify their intervention, though the factors served a second function of narrowing the ways in which others could use Kosovo as a precedent. But virtually no NATO state argued that the intervention was lawful, largely because the Charter does not legalize state uses of force in this context.

President Bashar al Assad visits the Kremlin, October 2015 / Office of the President of Russia

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As the Lawfare readership knows, the United States and its NATO allies relied on a series of factors in 1999 to argue that NATO’s intervention in Kosovo was legitimate. They used these factors to justify their intervention, though the factors served a second function of narrowing the ways in which others could use Kosovo as a precedent. But virtually no NATO state argued that the intervention was lawful, largely because the Charter does not legalize state uses of force in this context. We seem to be in a similar position now, after last night’s airstrikes in Syria.

In March 1999, in a press briefing, then-spokesperson for the State Department James Rubin identified a variety of factors on which the United States and the NATO alliance more generally relied to justify the intervention. The U.S., Canadian, Slovenian, Dutch, French, and British representatives to the UN Security Council identified a few other legitimating factors during the Council debate on the Kosovo bombing the following day.

Back in 2013, Jack and I wrote separately here and here about the relevance of the Kosovo precedent in the Syria context. In the wake of the overnight airstrikes by the United States in Syria, it is worth revisiting the Kosovo factors in detail to see how the situation in Syria compares.

None of this is to argue that the United States should (or should not) have intervened in Syria. There are credible political and moral arguments on both sides. But it is to suggest that such an intervention, even if narrowly tailored, is very difficult to defend as consistent with international law. Therefore, the United States will have to make the case that the intervention bears moral legitimacy, and it has begun to do so using the same kinds of factor-based arguments we saw NATO member states use in Kosovo to defend the legitimacy of their intervention there.

Josh Rogin reports on the justifications provided by the Trump Administration, which rely on factors such as the widespread “carnage” in the Syrian conflict, the use of chemical weapons against civilians over several years, Syria’s repeated violations of international law, and the idea that Assad’s use of chemical weapons “presents a clear threat to regional stability and security as well as the national security interests of the United States [and] our allies.” The Trump Administration has not asserted that its strikes were legal under international law.

The following is a list of factors that the United States and other NATO allies used in their public statements and in the Security Council debate to justify force in Kosovo. Under each factor, I consider how the situation in Syria compares.

1. The offending state was engaged in widespread and serious violations of international law.

This is true in Syria. The Assad regime has engaged in persistent violations of the laws of armed conflict, including the principles of distinction and proportionality. (Beth Van Schaack details some of those violations here.) Assad also has used chemical weapons such as chlorine gas and nerve agents against his population, which violates (among other things) the Chemical Weapons Convention. (The Security Council mandated that Syria join that Convention in 2013.) Many find the use of chemical weapons particularly revolting, and to this extent may view the Assad regime’s violations of international law as worse than Slobodan Milosevic’s.

2. The offending state’s forces used excessive and indiscriminate force.

Syrian forces have used excessive and indiscriminate force in the conflicts with various rebel groups. Assad has conducted an extremely bloody war that has often targeted civilian objects without justification, including hospitals and schools.

3. The offending state failed to comply with multiple U.N. Security Council Resolutions and other international legal instruments.

In the Kosovo context, the United States highlighted that the Federal Republic of Yugoslavia (FRY) failed to comply with a series of U.N. Security Council resolutions, including UNSCR 1199 and 1203, which recognized that the threat to Kosovo represented a threat to peace and security in the region. The United States also identified the FRY’s failure to comply with its agreements with the OSCE and NATO, the goals of which were to verify FRY compliance with UNSCR demands. The FRY also failed to comply with its obligation to cooperate with the International Criminal Tribunal for the Former Yugoslavia.

Assad’s government is in a similar posture similar to that of the FRY in 1999. Assad’s most palpable failure to comply with multilateral legal commitments has been his failure to comply with existing UNSCRs, including UNSCR 2254 (2015) (demanding that the parties to the conflict “cease any attacks against civilians and civilian objects as such, including attacks against medical facilities and personnel, and any indiscriminate use of weapons”) and 2268 (2016). The FRY was subject to more, and more direct, obligations under UNSCRs, as well as a clear finding by the Security Council that the situation posed a threat to peace and security in the region. But both actors flouted Security Council demands.

4. The offending state refused to negotiate to resolve the issue peacefully.

In the Kosovo situation, the FRY refused to accept and sign the Rambouillet accords, although the Kosovar Albanians signed them. Various NATO states employed this as a factor indicating that the failure to achieve peace fell squarely on Milosevic’s shoulders.

The Assad government and armed opposition groups reached a ceasefire in December 2016, brokered by Russia and Turkey. But it has been fragile, and both sides seem periodically to have violated it.

5. There were prospects of a wider conflict, and refugee flows threatened the stability of the region.

The Kosovo conflict had generated about 250,000 internally displaced persons and refugees by the time NATO decided to intervene. The flows largely remained in Europe’s back yard, including in Macedonia and Albania.

The Syrian conflict has produced IDPs and refugee flows on a far more significant scale. By some counts, there are 10.8 million Syrian IDPs and refugees. Further, these individuals have journeyed well outside of the region. However, perhaps one should ask a narrower question: did Assad’s recent use of chemical weapons alone stimulate more flows? The answer to that question is unclear.

6. There was a build-up of government forces in way that foreshadowed a pending attack.

In Kosovo, NATO states were concerned that Serb forces were massing in Kosovo and “giving every indication of conducting a new offensive against Kosovar Albanians,” which lent a temporal urgency to NATO’s intervention. I am unaware of evidence suggesting a similar build-up of government forces that would portend a new offensive, though the use of chemical weapons may well signal Assad’s revived interest in using such weapons again in the near future.

7. Observers and humanitarian workers in the offending state faced threats.

In Kosovo, there were threats to the safety of international observers and humanitarian workers. (It is not clear from the statements by NATO states how important it was that these workers had foreign nationalities.) In the Syria conflict, Syrian humanitarian workers, including members of the Syrian Red Crescent, seem to be bearing the bulk of the threat and harm. Several Syrian humanitarian workers died during their efforts to respond to the most recent chemical weapons attack.

8. The intervention involved a unity of action by a variety of states.

The military intervention in Kosovo was multilateral: NATO as a (then) 19-state organization decided collectively to intervene. The intervention also garnered multilateral political support from the European Union and the Organization for Security and Cooperation in Europe.

Although states and NGOs alike have condemned Assad’s actions—particularly his use of chemical weapons—to date no states have affirmatively supported the idea of military force to sanction Assad. In fact, both France and Britain have indicated a lack of interest in military options, with the French foreign minister urging the “resumption of Syria peace talks” and wanting to see President Assad's government prosecuted over its alleged use of chemical weapons but cautioning against “new military interventions.” (In 2013, the UK parliament voted against then-Prime Minister David Cameron’s proposed use of military force against Assad to deter further use of chemical weapons. PM Theresa May said yesterday that she has no plans to take military action against Assad.)

Unilateral action by the United States in Syria would put the intervention on starkly different footing than the Kosovo intervention.

9. Force must be a last resort, after other options have been exhausted.

This factor is always difficult to judge, but one could compile a long list of non-forcible (and to date unsuccessful) efforts that states have undertaken to help resolve the Syria conflict and to reduce the chance that Assad would use chemical weapons. There have been three efforts at ceasefires; an agreement between Assad, Russia, and the United States to destroy Syria’s chemical weapons and allow unfettered access by inspectors to Syrian sites; and several UN envoys. None has succeeded at ending the violence. To date, Russia has blocked action in the Security Council, though it signaled today (maybe genuinely, maybe disingenuously) that its support for Assad is not unconditional.


Overall, many of the factors that were present in the Kosovo intervention are present again in Syria today. One factor that gives a military intervention particular legitimacy is Assad’s repeated and horrific use of chemical weapons, even in the face of purported disarmament and adherence to the CWC. Another element that might affect third parties’ reactions is the scope of the intervention: states presumably will respond differently to narrow, targeted strikes directed at the Syrian air force’s capabilities than they would to a broad use of force against much of the Syrian government’s military forces and infrastructure. But the one factor that makes any kind of U.S. military intervention starkly different from the Kosovo context is the lack of multilateral support for and participation in such action. This lack of support suggests that many states do not believe that they have exhausted all non-forcible options, cannot envision what a successful military intervention would look like, believe that intervention would be unlawful, or lack the political will to intervene.

Ashley Deeks is the Class of 1948 Professor of Scholarly Research in Law at the University of Virginia Law School and a Faculty Senior Fellow at the Miller Center. She serves on the State Department’s Advisory Committee on International Law. In 2021-22 she worked as the Deputy Legal Advisor at the National Security Council. She graduated from the University of Chicago Law School and clerked on the Third Circuit.

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