National position of the United States of America (2012)

Introduction
This is the national position of the United States of America on international law applicable to cyber operations. The position has been presented by Harold Hongju Koh, Legal Advisor of the US Department of State, during the USCYBERCOM Inter-Agency Legal Conference at Ft. Meade, Maryland on 18 September 2012.

Applicability of international law
 "[...]international law principles do apply in cyberspace. Everyone here knows how cyberspace opens up a host of novel and extremely difficult legal issues. But on this key question, this answer has been apparent, at least as far as the U.S. Government has been concerned. Significantly, this view has not necessarily been universal in the international community. At least one country has questioned whether existing bodies of international law apply to the cutting edge issues presented by the internet. Some have also said that existing international law is not up to the task, and that we need entirely new treaties to impose a unique set of rules on cyberspace. But the United States has made clear our view that established principles of international law do apply in cyberspace." 

Use of force
 "Cyber activities may in certain circumstances constitute uses of force within the meaning of Article 2(4) of the UN Charter and customary international law. In analyzing whether a cyber operation would constitute a use of force, most commentators focus on whether the direct physical injury and property damage resulting from the cyber event looks like that which would be considered a use of force if produced by kinetic weapons. For example, cyber activities that proximately result in death, injury, or significant destruction would likely be viewed as a use of force. In assessing whether an event constituted a use of force in or through cyberspace, we must evaluate factors including the context of the event, the actor perpetrating the action (recognizing challenging issues of attribution in cyberspace), the target and location, effects and intent, among other possible issues. Commonly cited examples of cyber activity that would constitute a use of force include, for example, (1) operations that trigger a nuclear plant meltdown, (2) operations that open a dam above a populated area causing destruction, or (3) operations that disable air traffic control resulting in airplane crashes. Only a moment’s reflection makes you realize that this is common sense: if the physical consequences of a cyber attack work the kind of physical damage that dropping a bomb or firing a missile would, that cyber attack should equally be considered a use of force." 

Self-defence and armed attack
 "A state’s national right of self-defense, recognized in Article 51 of the UN Charter, may be triggered by computer network activities that amount to an armed attack or imminent threat thereof. As the United States affirmed in its 2011 International Strategy for Cyberspace, “[w]hen warranted, the United States will respond to hostile acts in cyberspace as we would to any other threat to our country.”

"[...]the United States has for a long time taken the position that the inherent right of self-defense potentially applies against any illegal use of force. In our view, there is no threshold for a use of deadly force to qualify as an “armed attack” that may warrant a forcible response. But that is not to say that any illegal use of force triggers the right to use any and all force in response—such responses must still be necessary and of course proportionate. We recognize, on the other hand, that some other countries and commentators have drawn a distinction between the “use of force” and an “armed attack,” and view “armed attack”—triggering the right to self-defense—as a subset of uses of force, which passes a higher threshold of gravity." 

International humanitarian law (jus in bello)
 "In the context of an armed conflict, the law of armed conflict applies to regulate the use of cyber tools in hostilities, just as it does other tools. The principles of necessity and proportionality limit uses of force in self-defense, and would regulate what may constitute a lawful response under the circumstances. There is no legal requirement that the response to a cyber armed attack take the form of a cyber action, as long as the response meets the requirements of necessity and proportionality." 

Military objectives
 "The principle of proportionality prohibits attacks that may be expected to cause incidental loss to civilian life, injury to civilians, or damage to civilian objects that would be excessive in relation to the concrete and direct military advantage anticipated. Parties to an armed conflict must assess what the expected harm to civilians is likely to be, and weigh the risk of such collateral damage against the importance of the expected military advantage to be gained. In the cyber context, this rule requires parties to a conflict to assess (1) the effects of cyber weapons on both military and civilian infrastructure and users, including shared physical infrastructure (such as a dam or a power grid) that would affect civilians; (2) the potential physical damage that a cyber attack may cause, such as death or injury that may result from effects on critical infrastructure; and (3) the potential effects of a cyber attack on civilian objects that are not military objectives, such as private, civilian computers that hold no military significance, but may be networked to computers that are military objectives."

"As you all know, information and communications infrastructure is often shared between state militaries and private, civilian communities. The law of war requires that civilian infrastructure not be used to seek to immunize military objectives from attack, including in the cyber realm. But how, exactly, are the jus in bello rules to be implemented in cyberspace? Parties to an armed conflict will need to assess the potential effects of a cyber attack on computers that are not military objectives, such as private, civilian computers that hold no military significance, but may be networked to computers that are valid military objectives. Parties will also need to consider the harm to the civilian uses of such infrastructure in performing the necessary proportionality review. Any number of factual scenarios could arise, however, which will require a careful, fact-intensive legal analysis in each situation." 

Legal review of cyber weapons
 "States should undertake a legal review of weapons, including those that employ a cyber capability. Such a review should entail an analysis, for example, of whether a particular capability would be inherently indiscriminate, i.e., that it could not be used consistent with the principles of distinction and proportionality. The U.S. Government undertakes at least two stages of legal review of the use of weapons in the context of armed conflict: first, an evaluation of new weapons to determine whether their use would be per se prohibited by the law of war; and second, specific operations employing weapons are always reviewed to ensure that each particular operation is also compliant with the law of war." 

Sovereignty
 "States conducting activities in cyberspace must take into account the sovereignty of other states, including outside the context of armed conflict. The physical infrastructure that supports the Internet and cyber activities is generally located in sovereign territory and subject to the jurisdiction of the territorial state. Because of the interconnected, interoperable nature of cyberspace, operations targeting networked information infrastructures in one country may create effects in another country. Whenever a state contemplates conducting activities in cyberspace, the sovereignty of other states needs to be considered." 

Attribution
 "[...]cyberspace significantly increases an actor’s ability to engage in attacks with “plausible deniability,” by acting through proxies. I noted that legal tools exist to ensure that states are held accountable for those acts. What I want to highlight here is that many of these challenges — in particular, those concerning attribution — are as much questions of a technical and policy nature rather than exclusively or even predominantly questions of law. Cyberspace remains a new and dynamic operating environment, and we cannot expect that all answers to the new and confounding questions we face will be legal ones." 

Attribution
<section begin=US_2012 attribution /> "States are legally responsible for activities undertaken through “proxy actors,” who act on the state’s instructions or under its direction or control. The ability to mask one’s identity and geography in cyberspace and the resulting difficulties of timely, high-confidence attribution can create significant challenges for states in identifying, evaluating, and accurately responding to threats. But putting attribution problems aside for a moment, established international law does address the question of proxy actors. States are legally responsible for activities undertaken through putatively private actors, who act on the state’s instructions or under its direction or control. If a state exercises a sufficient degree of control over an ostensibly private person or group of persons committing an internationally wrongful act, the state assumes responsibility for the act, just as if official agents of the state itself had committed it. These rules are designed to ensure that states cannot hide behind putatively private actors to engage in conduct that is internationally wrongful." <section end=US_2012 state responsibility />

[...]

"[..]cyberspace significantly increases an actor’s ability to engage in attacks with “plausible deniability,” by acting through proxies. I noted that legal tools exist to ensure that states are held accountable for those acts. What I want to highlight here is that many of these challenges — in particular, those concerning attribution — are as much questions of a technical and policy nature rather than exclusively or even predominantly questions of law. Cyberspace remains a new and dynamic operating environment, and we cannot expect that all answers to the new and confounding questions we face will be legal ones." <section end=US_2012 attribution />