Editor's Note: (Laurie Blank is clinical professor of law and director of the International Humanitarian Law Clinic at the Emory School of Law. She has authored and co-authored numerous publications, including "International Law and Armed Conflict: Fundamental Principles and Contemporary Challenges in the Law of War." Geoffrey S. Corn is professor of law at South Texas College of Law and co-author of "The Law of Armed Conflict: An Operational Perspective," among other publications.)
(CNN) U.S. Secretary of State John Kerry said Thursday what already seems obvious: ISIS is committing genocide against the Yazidis and other minority groups in Iraq and Syria.
ISIS atrocities surely deserve every form of condemnation the international community can muster. So what took so long? After all, Congress was quicker to act, voting unanimously to label ISIS atrocities as genocide in a nonbinding resolution earlier this week. But Congress has greater freedom of action here: A congressional resolution has persuasive moral force but does not trigger an obligation to act. A statement by the president or his secretary of state, on the other hand, is a different story, explaining the additional caution and deliberation many have criticized.
The term "genocide" is not a vague assignation to throw at every atrocity that shocks the conscience. Rather, genocide is a legal term connoting a certain crime -- a characterization that has very specific legal and political implications to which the Obama administration was correct to give due deliberation. When a government invokes this term to characterize a humanitarian crisis, it is triggering certain obligations. Most significantly, the Convention on the Prevention and Punishment of the Crime of Genocide requires states to take measures to prevent and punish the crime.
Genocide is the "crime of crimes," the most heinous of international crimes. And yet while genocide is the ultimate atrocity, not every atrocity amounts to genocide -- for good reason. Applying the term loosely risks diluting its moral, legal and political weight.
Genocide is the commission of certain acts with the intent to destroy, in whole or in part, a national, ethnic, religious or racial group: killing, causing serious bodily or mental harm, deliberately inflicting conditions calculated to bring about the destruction of the group, imposing measures to prevent births or forcibly transferring children to another group.
In condemning the genocide against Bosnian Muslims at Srebrenica, the International Criminal Tribunal for the former Yugoslavia explained that genocide is uniquely "horrific in scope; its perpetrators identify entire human groups for extinction." It is a crime against all of humanity, because "those who devise and implement genocide seek to deprive humanity of the manifold richness its nationalities, races, ethnicities and religions provide."
The stringent requirements to prove genocide thus preserve the singular opprobrium it deserves and also "guard against a danger that convictions for this crime will be imposed lightly," according to the tribunal.
Genocide is thus distinguishable from other international crimes, in particular through the requirement of specific intent: The perpetrators must have an actual objective to destroy a particular group, in whole or in part. In addition, the victims must also be a national, ethnic, religious or racial group, not merely any group or collection of victims.
As a result, not all heinous or even widespread atrocities qualify as genocide. But the fact that atrocities -- such as the widespread brutal attacks on civilians and use of sexual slavery in Sierra Leone or the Syrian government's mass shooting of unarmed protesters in the spring of 2011 -- do not meet the definition of genocide does not mean they are unimportant or not criminal.
Such widespread or systematic attacks directed against any civilian population are crimes against humanity, one of the most severe international crimes and most important tools in the arsenal of international criminal justice. The difference is that crimes against humanity do not require a specific intent to destroy and do not require that the victims be part of a specific national, ethnic, racial or religious group, the unique feature of genocide.
A determination of genocide raises important considerations for criminal, diplomatic and even military responses.
In the criminal arena, the Genocide Convention requires state parties to provide effective penalties for the crime of genocide and to undertake to punish perpetrators. Most significantly, under U.S. law, a designation of genocide importantly opens the door to prosecuting any person alleged to be responsible for this heinous international law violation, no matter where that crime was committed, even if the location, defendant and victims had no connection to the United States. Rarely used in the United States, this exercise of "universal jurisdiction" recognizes that some violations of international law are so egregious that they offend every nation equally, so all nations may bring violators to justice.
This is important, because invoking universal jurisdiction without a genocide characterization is difficult. The War Crimes Act, a federal law providing for the prosecution of war criminals, requires instead some link between the war crime and the United States. These jurisdictional constraints therefore place real limits on any attempts to prosecute an ISIS operative for war crimes -- a different crime than genocide -- against non-Americans in Iraq or Syria, for example.
For atrocities that constitute genocide, in contrast, the U.S. government has more tools to punish perpetrators, because it can prosecute any suspected perpetrator of genocide "present" in the United States (even "involuntarily"), no matter who the victims or where the crime was committed, enhancing opportunities for accountability.
Acknowledging genocide can enhance other tools as well. The United States, working through the U.N. Security Council, can request the International Criminal Court to investigate ISIS' alleged international crimes -- and the genocide designation provides the most powerful and persuasive foundation for such a claim. In addition, ongoing U.S. diplomatic efforts to isolate ISIS and cut off its access to resources will hopefully be strengthened, and ongoing efforts to degrade and destroy ISIS through military action sustained and bolstered.
This military arena is where we may find reasons for the government's apparently cautious deliberations on the genocide. The announcement of a genocide surely adds to the political and moral credibility of U.S. operations. And a growing international moral norm called the Responsibility to Protect declares that when a state manifestly fails to protect its own population (often by directly committing atrocities against them), the international community must step in to protect them and halt the crimes.
These are important moral imperatives. But international law offers no accepted legal basis to use military force to prevent or terminate a genocide without Security Council authorization. That is, the fact of genocide alone does not provide legal justification under international law for a state to use military force to stop that genocide.
The United States has asserted two international legal justifications for its operations against ISIS -- the consent of Iraq and the collective self-defense of Iraq -- so it is unlikely to be relying on a genocide characterization for legal justification.
Nevertheless, the rhetorical force of characterizing an ongoing atrocity as genocide undoubtedly creates an expectation that powerful nations will act decisively -- including with military force -- to prevent further suffering. For the United States, navigating the line between this powerful expectation and the legal justification for ongoing military action is akin to walking a tightrope, providing one explanation for caution in publicly condemning ISIS' acts as genocide.
But if characterizing ISIS atrocities as genocide is perceived as an international legal foundation for military action against the terror group, there is real danger of creating an opening for states to proclaim the existence of genocide and then use that as a pretext for military intervention perhaps driven by other goals and interests. In an international system that expressly seeks to prevent the use of force, enabling such pretexts is highly problematic.
ISIS is committing genocide. Indeed, the suffering ISIS has inflicted during its brutal reign is not only shocking but unconscionable at all levels. However, this designation, especially when made by the United States, has immense consequence, and therefore should only result from careful assessment and deliberation.
Such deliberation does not reflect a callousness or indifference by the United States, but must instead be acknowledged as adding great weight to the significance of the designation. It is precisely because this outcome was the result of careful assessment that it means so much, and there should be no doubt that Kerry knew exactly what it meant, both in terms of condemnation and obligation.
Join us on Facebook.com/CNNOpinion.
Read CNNOpinion's new Flipboard magazine.