Brian Cox on “Domestic and International Law Considerations Involved in Enforcing a No-Fly Zone Over Ukraine”

Today we have an interesting – and provocative – essay by Lawfire® contributor Brian L. Cox who examines the international and domestic law considerations in the event a decision was made to create a “no-fly zone” as Ukraine President Volodymyr Zelenskyy has sought. 

As you will see, he finds the international law issue rather straightforward, but the domestic law more complicated.  His insists that “a fundamental reevaluation of current understandings of the constitutional balance of war powers is desperately needed.”  That said, however, he makes this eye-opening statement:

Regardless of implications involving the constitutional balance of power, policymakers must unambiguously understand that, contrary to an assertion that is common among many advocates, imposing and enforcing a no-fly zone over Ukraine does not inherently constitute a “war” simply because U.S. military forces may become involved in active hostilities against Russia.

If you want to see how Brian comes to that and other conclusions in this thought-provoking essay, read on!

Domestic and International Law Considerations Involved in Enforcing a No-Fly Zone Over Ukraine

by Brian L. Cox

As the armed conflict in Ukraine continues to expand and intensify, debate involving whether military forces from countries in the West should enforce a no-fly zone over the territory will become ever more pressing. Earlier this month, President Volodymyr Zelenskyy of Ukraine criticized NATO for giving “the green light for further bombing of Ukrainian cities and villages, having refused to set up a no-fly zone.” Although some U.S. lawmakers have expressed support for the idea, many others have warned against the measure.

With the Biden administration describing the proposal as “not a good idea” because it would be “definitely escalatory” and “potentially put [the United States] in a place where we are in a military conflict with Russia,” it appears that imposing a no-fly zone over Ukraine is not currently an option. Taking the possibility of implementing and enforcing a no-fly zone off the table is a mistake, and the time to reverse course is now.

Professor Mark Nevitt recently offered a rational and persuasive argument to the contrary in a post on Just Security. The present contribution challenging this argument picks up where Nevitt leaves off in his cogent essay. While Nevitt sensibly calls for U.S. and allied policymakers to “remove any discussion of a Ukraine no-fly zone from the table as a credible policy option,” he begins this closing point with the qualification: “unless conditions in Ukraine fundamentally change.”

With reports emerging that Russia may be laying the groundwork for chemical weapons attacks that could be blamed on Ukrainians and is purposefully provoking Belarus to join Russia in the conflict, conditions in Ukraine can “fundamentally change” in a matter of mere minutes. Although President Biden recently warned that “Russia will pay a severe price if they use chemicals,” it is not clear that the threat of increased sanctions would be enough to deter an initial or continued use of chemical weapons given that the sanctions that are already in place have been described as the “most severe” ever levied against Russia.

In case conditions do take a drastic turn for the worse in Ukraine, resorting to military force – including by implementing a no-fly zone – must be a viable and credible option. The logistical and practical arrangements necessary for doing so would be immense, as Professor Nevitt correctly points out. Those preparations must be undertaken now, before a proverbial red line is crossed, in order for armed intervention to be a legitimate possibility.

Engaging in a military intervention is not a decision that should be taken lightly, and there is no indication thus far that policymakers in the United States or NATO would do so. As the crisis in Ukraine continues to unfold, there are a number of domestic and international law considerations that must be addressed if an armed intervention is to be a credible option. For the remainder of this essay, I intend to address the most pressing of these factors.

International Law Considerations Involved in Enforcing a No-Fly Zone

This is perhaps the most unambiguous aspect of the analysis – though the issue of neutrality adds a bit of complexity to the issue. As an initial matter, the dual international legal bases for providing assistance are clear. The UN Charter confirms in Article 51 that nothing in the treaty shall “impair the inherent right of individual or collective self-defence if an armed attack occurs.” There is, of course, no question that an armed attack has occurred and that Member States may invoke the inherent right of collective self-defense to intervene in Ukraine.

Likewise, President Zelenskyy has repeatedly appealed to governments in the West to “close the skies over Ukraine.” This is an unambiguous expression of the consent of the host nation to enforce a no-fly zone, which constitutes a second international law basis for an armed intervention. Authorization from the Security Council pursuant to Article 42 of the Charter is, of course, not a viable legal basis given that a member of the P5 is the aggressor in the armed conflict.

This leaves the issue of neutrality to address briefly before transitioning to consider the domestic law implications of the proposed no-fly zone. The law of neutrality has generated some interest of late in the context of providing weapons to assist Ukrainian armed forces in the conflict.

International law experts Brian Finucane, Wolff Heintschel von Heinegg, and Mike Schmitt, for example, have each appealed to the principle of qualified neutrality in separate blog posts to assert that Western governments can provide weapons to Ukraine without violating neutral status since Russia is the aggressor in the conflict. While Finucane correctly cites to a 1941 speech by the then-US Attorney General to support the principle of qualified neutrality, the Department of Defense Law of War Manual is likewise correct to point out that Attorney General Jackson’s remarks were controversial at the time.

As Finucane also notes accurately in his essay, “Moscow’s analysis may be different” in the context of providing weapons to Ukraine. While he observes that the contemporary use of force is governed by the UN Charter, Russia’s pretextual claim that “self-defence against the threats posed to us and against an even greater calamity” in Ukraine provides at least the façade of Charter compliance.

Given that Russia has now announced that convoys carrying arms to Ukraine will be considered “legitimate targets,” there is no question that the aggressor believes Western governments do not enjoy neutral status in the conflict. This is the case whether the West simply continues provide materiel (and material) support to Ukraine or whether governments intervene in a more active role. The question now is how Moscow will respond, not whether Russia believes Western governments are neutral in the conflict.

This addresses the most salient issues involving the enforcement of a no-fly zone from an international law perspective. While these considerations are fairly straightforward, the potential legal basis in domestic law for an armed intervention in Ukraine involves a considerably more contentious analysis. From a domestic law perspective, war powers, authorization to use military force, and the very constitutional balance of power are at stake. As the following analysis demonstrates, the pivotal issue is what exactly qualifies as a “war in the constitutional sense.”

Defining a War in the Constitutional Sense

Identifying the branch with authority to implement and enforce a military intervention in Ukraine primarily implicates two central powers allocated to Congress by Article I of the Constitution – authority to declare war and to appropriate money – and presidential Article II authority as the chief executive and commander in chief of the armed forces. As a listing of notable deployments of U.S. military forces overseas” from 1798 to February 2022 recently published by the Congressional Research Service (CRS) observes, there are “hundreds of instances [in U.S. history] in which the United States has used its Armed Forces abroad in situations of military conflict or potential conflict or for other than normal peacetime purpose.” Of these “hundreds of instances,” Congress has formally declared war on only 11 specific occasions involving 5 armed conflicts in total.

This extensive history of armed intervention abroad in the absence of a formal declaration of war suggests that unilateral executive authority to employ force in situations short of war has both broad and deep historical roots. It also highlights the vital importance of distinguishing a “war” requiring a congressional declaration from the more general category of employing military force in armed conflict abroad.

As Brian Finucane points out while analyzing the attack by U.S. forces that killed Qassem Soleimani in 2020, a central analytical component that emerged in executive branch parlance as early as the Clinton administration is to evaluate whether a proposed use of force constitutes a “war in the constitutional sense.” Although the administration of George W. Bush adopted a constitutional interpretation that vested perhaps even more extensive authority in the executive, the administrations of Presidents Clinton, Obama, and Trump have assessed the “nature, scope, and duration” of a proposed use of force to determine whether the president has unilateral authority to order the employment of armed force.

This “nature, scope, and duration” test has been described and implemented as an intensely “fact-specific assessment.” As a presidential candidate in 2019, Joe Biden observed that the “nature, scope, and duration” test “has served us [the United States government] well,” and his administration’s use of force analysis has been routinely consistent with that of his recent presidential predecessors.

With a fact-specific assessment that addresses factors such as the nature, scope, and duration utilized to determine whether a proposed use of force amounts to “war in the constitutional sense,” it is centrally important to seek enhanced clarity involving what exactly does – and does not – constitute a “war.”

Armed Conflict: War by Another Name?

Although the DoD Law of War Manual notes that “there is no single legal definition of ‘war,’ hostilities,’ or ‘armed conflict,’” two central historical references incorporated by the Manual are useful in the endeavor of determining whether a use of force qualifies as a war in the constitutional sense based on the nature, scope, and duration of force contemplated.

One reference cited by the Manual is the oft-quoted definition for “war” drawn from Oppenheim’s 1906 International Law treatise: “War is a contention between two or more States through their armed forces, for the purpose of overpowering each other and imposing such conditions of peace as the victor pleases.” (emphasis added) In the same footnote, the Manual also cites to and quotes a passage of the 1863 Lieber Code, which observes: “Public war is a state of armed hostility between sovereign nations or governments…whose constituents bear, enjoy, and suffer, advance and retrograde together, in peace and in war.” (emphasis added)

Drawing from these central historical definitions – particularly the passages with emphasis above – and applying them to specific examples of the use of force presents at least three factors that are useful for ascertaining whether the nature, scope, and duration of an armed conflict in general suggest that it should qualify as a “war” more specifically. Although a full analysis of all notable deployments of U.S. military forces from 1798 to today is beyond the scope of this essay, for analytical purposes I will contrast U.S. involvement in World War II with the periodic, limited drone strikes carried out by the Biden (and previous) administration against armed militia groups in Syria near the border with Iraq. Most contemplated or actual uses of armed force, including the proposed enforcement of a no-fly zone over Ukraine, will fall somewhere on a spectrum between these two poles in terms of nature, scope, and duration.

One central characteristic that separates war from armed conflict conceptually is the extent to which the resources of the sovereign may be expected to be involved in the “contention between” States. For a conflict such as World War II, during which the full economic, industrial, and sociopolitical spectrum of America were shifted to support the war effort, it is reasonable to expect that Congress should decide whether to declare war in the constitutional sense. This is not necessarily the case when deciding whether to authorize a limited strike from a drone over the Syrian frontier given that, to draw from Lieber’s definition, American constituents as a whole are unlikely to “bear, enjoy, and suffer, advance and retrograde together” as a result of that decision.

For a similar reason, another characteristic that appears to make “war” a special subset of the more general category of “armed conflict” is that any person or object in America that the adversary determines constitutes a military objective will be subject to attack – whether at home or abroad – if the opponent likewise declares or otherwise engages in an actual “war” against the United States. The extent to which America as a whole will “bear, enjoy, and suffer” together as a result of a limited drone strike in Syria is vastly different than entering a conflict with the industrialized Axis Powers of World War II.

Finally, because an actual war between sovereigns typically ends pursuant to a legally-binding negotiated settlement, commonly referred to as a general armistice, the outcome of the war can be expected to have sweeping consequences for American constituents as a whole. As the glossary to the Online Casebook published by the ICRC notes, a belligerent Party may denounce an armistice and immediately restart hostilities if an opposing Party commits a “serious violation” of the agreement. This characteristic of “war” means that the “conditions of peace” – to draw from Oppenheim’s definition – agreed at the conclusion of hostilities can have implications for American constituents as a whole in a way that, for example, a limited drone strike in the Syrian frontier would not.

Where does implementation of a no-fly zone over Ukraine fit in this framework? Like most actual or contemplated uses of armed force abroad, determining precisely where a no-fly zone fits on the spectrum would depend on the conditions placed on the intervention and on the scope of the forces assigned to implement it. However, the fact that the adversary is a country with an advanced, industrialized military that could escalate the “contention” beyond Ukraine and the surrounding area does not necessarily mean the armed conflict inherently qualifies as a “war” in the constitutional sense.

Addressing the Perennial Struggle for the Constitutional Balance of War Powers

Readers familiar with the issue of constitutional separation of powers in the context of armed conflict will note that the analysis thus far has not addressed the War Powers Resolution (WPR) and the congressional “authorization” to use military force (AUMF). While the WPR and a separate congressional “authorization” such as the 2001 and 2002 AUMF are important to the discussion, the threshold matter that must be addressed first and that remains unresolved is what exactly constitutes a “war in the constitutional sense.” This is the case because both categories of legislative authority are beset by unresolved constitutional questions.

Section 5(b) of the WPR purports to require the president to “terminate any use of United States Armed Forces” within 60 days after introducing U.S. forces “into hostilities or into situations where imminent involvement in hostilities is clearly indicated by the circumstances” unless Congress declares war or grants an extension. However, it is by no means clear that every conceivable example of introducing U.S. armed forces into hostilities or potentially imminent hostilities that is not accompanied by a declaration of war constitutes a “war in the constitutional sense” such that Article I authority is implicated. As a CRS report on the topic succinctly notes, “Every President since the enactment of the War Powers Resolution has taken the position that it is an unconstitutional infringement on” executive authority.

Similarly, an “authorization” to use military force such as the 2001 and 2002 congressional resolutions addressing entities involved in the September 11, 2001 attacks and enforcing UN Security Council resolutions in Iraq, respectively, can be thought of as a political expression of support rather than an outright requirement for the use of force by the executive. That both such AUMF resolutions draw on the War Powers Resolution for authority, notwithstanding that the WPR itself rests on uncertain constitutional grounds, is further evidence that the threshold matter of determining what constitutes a “war in the constitutional sense” is of primary and central importance.

Collectively, these considerations suggest that a fundamental reevaluation of current understandings of the constitutional balance of war powers is desperately needed. While it is common for lawmakers and advocates alike to assert that Congress must “reclaim” authority involving the use of force from the executive branch, an alternative interpretation of such efforts is that Congress has been “attempting to increase its policy-making role” at the expense of constitutional authority vested in the executive ever since adoption of the War Powers Resolution in 1974.

Regardless of implications involving the constitutional balance of power, policymakers must unambiguously understand that, contrary to an assertion that is common among many advocates, imposing and enforcing a no-fly zone over Ukraine does not inherently constitute a “war” simply because U.S. military forces may become involved in active hostilities against Russia.

Although Senator Chris Murphy recently expressed, for example, that a no-fly zone is “a bad idea and Congress would never authorize it,” the actual nature, scope, and duration of the intervention authorized by President Biden would determine whether the use of force constitutes a “war in the constitutional sense” in the first instance. Depending on the circumstances contemplated by the Biden administration, it will not matter that “Congress would never authorize” the executive to implement a no-fly zone since doing so may not require Article I constitutional powers.

Making Preparations Now to Allow Action When Needed

It may well turn out that refraining from direct military intervention is the prudent course of action. Russian forces have reportedly committed nearly all of their pre-staged combat power into the theater of operations, yet progress toward President Putin’s apparent strategic objectives has remained frustratingly elusive. Economic measures implemented weeks ago are wreaking havoc on the Russian economy, and civil unrest in response to the “special military operation” is emerging in previously unimaginable ways. If the Russian military campaign proves incapable of achieving Putin’s main objectives yet NATO stages a military intervention anyway, this could be used to rally domestic popular support in Russia. Likewise, direct military involvement by NATO risks an escalating armed conflict between nations with vast stocks of nuclear weapons.

Nonetheless, completely removing the possibility of military intervention from the range of options available to the United States and NATO gives Russia maximum flexibility when negotiating a truce and eventual armistice with Ukraine. Doing so also creates space for Russian forces to threaten or actually conduct chemical weapons attacks or nuclear power plant sabotage. An eventual siege of Kyev and other major Ukrainian population centers could drag on for months while populations in the besieged cities slowly starve to death.

Signaling a commitment to avoiding direct military intervention by NATO no matter the cost, which has been a strategic imperative so far, increases the likelihood that Russia will engage in conduct that would cross the proverbial red line in order to tip the scale in favor of the invader. If a no-fly zone or other direct military intervention is to be a viable option, planning and force posture must be adjusted now to allow for the option later.

In order for this to occur, the Biden administration must communicate to Congress and to the American electorate that the executive branch has exclusive authority to take action, consistent with longstanding precedent, as long as the “nature, scope, and duration” of the planned intervention does not rise to the level of a “war in the constitutional sense.” If Congress elects to prevent executive action, Article I appropriations authority can be used to block the proposal if sufficient political will exists to do so.

Unless and until that occurs, President Biden should exercise unilateral Article II constitutional authority to plan, prepare for, and if necessary engage in a direct military intervention in Ukraine. If the commander in chief ultimately declines to intervene based on the circumstances, all the better. However, the decision to refrain should be the product of a policy determination that intervention is not warranted, not a mistaken judgement that congressional approval is required as a matter of law.

Perhaps conditions in Ukraine will not fundamentally change, and if so a no-fly zone or other direct NATO military intervention may not be necessary. In case conditions do fundamentally change, though, the time to prepare for direct involvement is now. As long as the intervention does not constitute war in the constitutional sense, the decision – and the ultimate responsibility for that decision – must rest with just one person, not with 535 plus one

About the author: 

Brian L. Cox is is a doctoral candidate lecturer and J.S.D. candidate at Cornell Law School and a visiting scholar at Queen’s Law in Ontario. Brian retired in 2018 from the U.S. Army after 22 years of military service. He served as an airborne infantry soldier, combat camera operator, airborne infantry officer, and for seven years as a military legal advisor. His combat deployments include Iraq from 2003-2004 as a combat camera operator and Afghanistan from 2013-2014 as the chief of international and operational law for Regional Command-East in Afghanistan.

Brian also served as a military prosecutor, federal prosecutor, brigade judge advocate, and military magistrate while he was a military legal advisor. His military awards, decorations, and qualifications include the Ranger Tab, Senior Parachutist Badge, Pathfinder Badge, Air Assault Badge, Bronze Star Medal, Meritorious Service Medal, Basic and Advanced Collateral Damage Estimation Certification, Joint Firepower Certification, and Special Victim Unit Investigator Certification. Brian holds an LL.M. from Queen’s Law and a B.A. (International Relations) and J.D. from the University of North Carolina.

The views expressed by guest authors do not necessarily reflect the views of the Center on Law, Ethics and National Security, or Duke University.

Remember what we like to say on Lawfire®: gather the facts, examine the law, evaluate the arguments – and then decide for yourself!

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