This article is the latest in our Fog of Law series that examines the gray zones in international law and conflict that can be exploited by states. The series comes in advance of an expert workshop on the topic at the US Naval War College’s Stockton Center that Just Security is cosponsoring with the Naval War College and the International Committee of the Red Cross.

I’m privileged to have been invited to lead a workshop on the jus ad bellum on Tuesday, May 15 at the Naval War College in Newport, Rhode Island. The sponsors have asked me to say a few preliminary words to outline the sorts of issues we’ll be considering.

My notion of the “fog of law” is sketched out in a book I wrote by that title eight years ago. The “fog” refers, of course, to ambiguities that pervade the international rules governing when states are permitted to use force. That fog prevents policy-makers from knowing whether they would be within or beyond the outposts of the law when considering military options.  The fog is formed, initially, by uncertainties flowing from international law’s legitimating principle.

That principle is state consent. States are bound, we know from The Lotus (and arguably from simple observation), only by those rules that they accept. Obligation follows choice. But the notion of a voluntarist, consent-based system that is at the same time binding raises vexing questions. Why can a state not freely withdraw its consent? What if a state consents to differing, opposite rules? Sorting out state consent can then require choosing one expression of consent over another; this is the difficulty that emerges when state practice diverges from what an original rule permits. To which “rule” has the state in fact consented?

It’s tempting to skip over these more abstract questions and proceed directly to the concrete, workaday issues that confront governmental decision-makers. But we can’t ignore its foundation if we have any hope of assessing the coherence of the jus ad bellum. Putative primary rules must arguably be justified by, and measured against, secondary meta-rules that “make law, law.” The workshop will afford participants the chance to examine candidly, and off the record, the premises that underpin claims about the international rules governing when force may be used.

A starting point will be to consider the frank answer given by General Keith Alexander to the Senate Armed Services Committee on April, 2010, when he was nominated by President Obama to be Commander of the U.S. Cyber Command. Alexander said: “There is no international consensus on a precise definition of a use of force, in or out of cyberspace. Consequently, individual nations may assert different definitions, and may apply different thresholds for what constitutes a use of force.”

Alexander’s statement raises myriad questions. Is this an accurate description of the current law? If no authoritative interpreter exists and “use of force” in fact means anything any nation reasonably defines it to mean—even in realms other than cyberspace—does the law governing use of force have any meaning? And if “use of force” under Article 2(4) of the UN Charter is taken to mean the same thing as an “armed attack” under Article 51, isn’t the resulting fluidity a formula for legalizing use of force across-the-boards against multiple potential state and non-state actors—particularly in light of collective defense rights and responsibilities? What use of force, if any, does international law actually prohibit?

The original, paper rules are familiar. Their text is set out in Articles 2(4) and 51. The differing wording of those provisions raises numerous issues. Is the threshold under each identical, or do some uses of force not constitute armed attacks?  How low is the threshold? Is assassination prohibited, for example, or minor destructions of property that cause no casualties, or one-off drone strikes, or low-level cyber-intrusions? Are some uses of force permitted under the Charter if they are not directed against a state’s “territorial sovereignty or political independence”? What is the test for determining whether a given action constitutes a use of force? Should we look at means or effects? If no consensus exists, as Alexander suggests, is the default rule the Lotus’s freedom principle, which accords states unfettered freedom of action?

The fog thickens: Are the Charter rules even the right rules to parse? Is there, for example, an altogether different legal regime governing intervention in a civil war, such as that still raging in Syria; did the old rules of customary international law concerning non-intervention survive ratification of the Charter (or, for that matter, the Spanish Civil War)? Are pre-Charter “reprisals” now once again permitted in response to violations of at least some rules of international law, such as those prohibiting the use of chemical or biological weapons? For that matter, are there rules in the international system to which states have not actually consented but by which they’re legally bound—and if so, are use of force rules among them? Might just war theory provide part of such a framework?

The text of Article 51, unlike Article 2(4), makes no reference to threats; the textual predicate for permissible use of defensive force is an armed attack, not the threat of one. Does the Charter’s text therefore require an actual armed attack before defensive force is permitted? Must defending forces in a putative Pearl Harbor wait to respond until the bombs literally begin to fall? What presumptions may a state reasonable draw in the face of indeterminate intent or capability on the part of a potential adversary? Does Article 51 prohibit the use of defensive force against, say, a state that launches a drone into the territory of another state? How is the latter state to know whether the drone’s controller is “preparing the battlefield” for an armed attack or is merely conducting surveillance—or whether the drone itself is armed? Is it a use of force, or an armed attack—or something else—to plant on an another government’s computers dual-use malware that could merely log keystrokes—or that could, when activated to another level, erase the entire storage facility in which it sits, or de-activate power grids, or launch a missile? Under conditions of empirical uncertainty, how does international law allocate the burden of risk?

These questions, and many like them, arise from paper rules. But what are the working rules of the jus ad bellum? Beyond the ritualistic talking points declaiming states’ undying respect for international law, what rules do decision-makers actually feel bound by? The 1945 paper rules were grounded on the expectation that the Security Council would become a muscular constabulary overseeing standing or standby forces that could move swiftly to maintain or restore international peace and security—a vision that of course never materialized. Have the governing rules changed over time in response to changed circumstances and divergent state practice? If the starting point is indeed state consent, did states—do states—consent to the text of the UN Charter as originally formulated, or to a treaty that may differ drastically from the one ratified in San Francisco? Does state practice—not opinio juris, but actual state practice—support the claim that defensive force is now permissible in response to the imminent threat of an armed attack? Does the rigid 1837 Caroline standard accurately reflect modern state practice? If the dam has in fact broken and a sea of conflicting practice has washed away the bright line of an armed attack, is preventive defensive force now permissible in the face of a grave and devastating attack that is not imminent but is nonetheless probable? How far has the original rule of Article 51 eroded?

The April, 2018 air strikes launched against Syria by the United States, Britain, and France raised many of these questions anew. Is humanitarian intervention by one state within another for the purpose of curbing certain human rights abuses now permissible—despite the continuing, vociferous objections to the concept earlier voiced by nations of the South and East? Was the British government’s legal rationale for the Syrian raid correct? Might the Russian government have claimed support from the same principle for its 2014 intervention in Crimea? If subsequent practice has eviscerated the Charter’s limits, why has its erosion stopped at humanitarian intervention and not continued to the point that seems implicit in General Alexander’s remark—at desuetude, the point at which the earlier Charter rules have been supplanted by a null-set rule that reinstates the Lotus’s freedom principle and recognizes the authority of each state to act as it will, without restriction? Is the massive number of violations by numerous states over an extended period of time evidence that they have withdrawn their consent to the original rules of the Charter? How much bite is realistically left in the Charter? Is it “utopian quibbling,” as Michael Walzer has argued, to dwell on the meaning of the Charter’s use-of-force rules? Think of the Bay of Pigs, the Dominican Republic, Grenada, Nicaragua, Panama, Kosovo—and, arguably, Iraq and the later stages of Libya: Was there ever a given military initiative that U.S. decision-makers desired to undertake but foreswore because they believed it would violate the Charter? Why do powerful states show so little interest in strengthening the rules that restrict the use of force? Faced with the Charter’s manifest failure to “save succeeding generations from the scourge of war,” might reformers now find it more useful to work to establish the background political conditions needed to make the rules work—before pushing to adopt more paper rules?

These questions, I hope, will serve as a starting point. My own answer to some of them is summarized in an April 30 post on Lawfare, responding to an April 16 post by Jack Goldsmith. Goldsmith argues that it’s misleading or meaningless to inquire whether the U.N. Charter’s use-of-force rules are law; I disagree, and suggest that they are not. The distinguished participants in our workshop will no doubt pose further, deeper questions. I look forward to our discussion.

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