Recently, Russian aircraft ‘buzzed’ a US Navy ship and ‘barrel rolled’ over a US Air Force plane above the Baltic Sea. The fallout cast a distracting pall over last week’s NATO-Russia Council meeting in Brussels. The first such conference since Russia annexed Crimea, it was intended to defuse tensions between the alliance and Russia and allow dialogue on issues like Ukraine and Syria. Instead, the meeting “failed to make any apparent progress,” including on avoiding future military encounters between Russia and NATO.

Pointing out that Russia’s antics over the Baltic Sea violated international law may seem like a drop in the ocean compared to the serious humanitarian consequences of the crises in Crimea and eastern Ukraine, as well as in places like Yemen, Syria, and Afghanistan. Russia’s aerial acrobatics in the Baltic are almost comical, as if an attempt to provide source material for the ‘bad guys’ in the Top Gun sequel. They are less entertaining, however, in their context. Part of a string of similar incidents, recent events demonstrate Russia’s apparent intent on aggravating relations with the West. The timing — coming shortly before a meeting to de-escalate tensions — does not appear coincidental.

The Russian government has imprecisely invoked international law to justify its behavior. For those who believe international law provides the best framework to ensure interstate disputes are resolved short of force, it is important to draw attention to specific violations and relevant international legal principles, but to do so accurately and with precision. This is particularly true for actions that risk encouraging escalation even if they themselves do not reach the use of force threshold, or actions that seem deliberately intended to intimidate or provoke a response. The United States has lodged formal protests with Moscow and the events in the Baltic were apparently raised during the NATO-Russia Council meeting. However, in public discourse, NATO’s focus has mostly been on Russia’s lack of professionalism, only hinting at the underlying violations of law. In the interest of clarifying the role of international law in the dispute, I explain how Russia violated its international obligations by performing ‘simulated attack profile strafing runs’ over a US ship in international waters and a ‘barrel roll’ over a US reconnaissance plane in international airspace.

The 2016 Cook Incident and the ‘Barrel Roll’

Video from mid-April shows Russian aircraft performing close overflights of the USS Donald Cook (DDG-75), an Arleigh Burke-class guided missile destroyer operating in the Baltic Sea. Russian Sukhoi Su-24 attack aircraft and one or more KA27 Helix helicopters conducted actions that a senior US defense official described as “more aggressive than anything we’ve seen in some time.”

The USS Cook was patrolling in support of US Sixth Fleet operations in Europe. Sailing in international waters after leaving the port of Gdynia, Poland, the Cook was preparing to conduct a joint training operation with a Polish helicopter. According to reports, the Cook was shadowed by a Russian intelligence-gathering ship. Russian aircraft made roughly twenty passes within 1,000 yards of the destroyer at an estimated altitude of 100 feet. The following day, Russian helicopters repeatedly circled the Cook, taking photographs. The Su-24s returned and made roughly a dozen more passes of the ship, flying an estimated thirty feet from the Cook’s superstructure in a “simulated attack profile.” US officials described these passes as mock “strafing runs,” as they followed a recognizable flight pattern used for diving attacks on ground targets. The Russian planes did not respond to attempts by the American crew to contact them.

The US Embassy in Moscow formally protested. Within days of the Cook incident, a Russian Su-27 intercepted a US Air Force RC-135 reconnaissance plane flying in international waters in the Baltic. According to US European Command (EUCOM), the Su-27 came within fifty feet of the RC-135’s wingtip and performed a left-to-right ‘barrel roll’ over the top of the aircraft.

US and Russian Responses

While the word “aggression” is bandied about with increasing frequency in regard to incidents at sea, the flyovers are not the sort of “threat or use of force” that implicates Article 2(4) of the UN Charter. For one, it seems to have been apparent early on that the Russian aircraft were not armed with the anti-ship missiles they are equipped to carry. Second, an attack by Russian aircraft on a ship would be initiated from much farther away. Finally, interactions between naval forces at sea during peacetime have a long history.

This explains the disciplined restraint shown by the Cook, despite the unusually provocative actions of the Russian aircraft, which ostensibly were intended to send a message about US defense commitments in Eastern Europe and the presence of NATO forces near the Russian exclave of Kaliningrad. The “strafing runs” in particular appear to be an attempt to intimidate Poland. Under US rules of engagement or as a form of unit self-defense, responding with force may have been permissible. The Cook did not use force because, in the words of retired US Navy Captain Rick Hoffman, “you don’t get to kill people just because they’re being annoying.”

States should, however, highlight when such ‘annoyances’ are violations of international law. US responses have hinted at Russia’s lack of respect for the international legal order, but mostly emphasized that Russia’s actions were dangerous and unprofessional. Following the Cook incident, EUCOM said:

We have deep concerns about the unsafe and unprofessional Russian flight maneuvers. These actions have the potential to unnecessarily escalate tensions between countries, and could result in a miscalculation or accident that could cause serious injury or death.

The White House added:

There were reports of Russian planes flying dangerously close to a US naval ship and a Polish aircraft. This incident, you won’t be surprised to hear, is entirely inconsistent with the professional norms of militaries operating in proximity to each other in international waters…. Any peacetime military activity must be consistent with international norms and conducted with due regard for the rights of other nations and the safety of other aircraft.

Dangerous and unprofessional indeed, yet it is necessary to emphasize Russia breached specific international legal obligations in light of the Russian government’s response. Igor Konashenkov, spokesman for the Russian Defense Ministry, was quick to defend Russia’s actions, claiming Russia acted “in accordance with international rules.” In a prime attempt at lawfare, he invoked international law of the sea principles by claiming “[t]he principle of freedom of navigation for the US destroyer, which is staying in close proximity to a Russian naval base in the Baltic Sea, does at all not cancel the principle of freedom of flight for Russian aircraft.” Secretary Kerry responded “we respect our freedom of navigation … and we are communicating to the Russians how dangerous this is.”

The response to the ‘barrel roll’ followed a similar pattern. Konashenkov said the Russian plane’s actions were in “strict conformity with international laws” and Secretary Kerry condemned the encounter as dangerous and provocative. NATO Secretary General Jens Stoltenberg cited Russia’s illegal annexation of Crimea as a basis for an increased NATO presence in Eastern Europe. In response, Russia’s Ambassador to NATO, Aleksandr Grushko, obfuscated with imprecise and irrelevant international legalese, arguing the presence of the Cook in the Baltic allowed Russia to take “all necessary measures [and] precautions to compensate US attempts to use military force.”

INCSEA and Pacta Sunt Servanda

In addition to undermining freedom of navigation in international waters and international airspace through its aircraft’s dangerously aggressive behavior, Russia’s forces violated a specific legal agreement and another fundamental international law norm. Last week’s antics are the exact sort of behavior prohibited under the terms of the 1972 Incidents at Sea Agreement (INCSEA), a treaty between the US and the USSR, to which the Russian Federation succeeded as a party. Article IV of INCSEA states:

Commanders of aircraft of the Parties shall use the greatest caution and prudence in approaching aircraft and ships of the other Party operating on and over the high seas, in particular, ships engaged in launching or landing aircraft, and in the interest of mutual safety shall not permit: simulated attacks by the simulated use of weapons against aircraft and ships, or performance of various aerobatics over ships, or dropping various objects near them in such a manner as to be hazardous to ships or to constitute a hazard to navigation.

Russia’s “strafing runs” against the Cook are a violation of INCSEA’s prohibition on simulated attacks and “various aerobatics.” This is supported by a clear reading of the text and context of INCSEA, following the interpretive framework of Article 31 of the Vienna Convention on the Law of Treaties (VCLT). INCSEA constitutes a treaty under international law, as defined by Article 2(1)(a) of the VCLT and the standard the ICJ set out in its 1994 Qatar v. Bahrain ruling on jurisdiction and admissibility.

Russia may perhaps argue that the ‘barrel roll’ falls outside the scope of the “various aerobatics” prohibited under Article IV of INCSEA, since it occurred over an aircraft and the text only explicitly forbids acrobatics “over ships.” However, the barrel roll fails to meet the requirement of “greatest caution and prudence” that Article IV imposes on commanders of aircraft approaching “aircraft … of the other Party operating on and over the high seas.”

Implicit in these direct violations of INCSEA are violations of a core legal principle. Konashenkov’s statement on “international rules” ignores the closest the international community has to a Golden Rule: pacta sunt servanda. Part of customary international law — and binding upon all states — the principle that agreements must be kept is enshrined in Article 26 of the VCLT, which reads “[e]very treaty in force is binding upon the parties to it and must be performed by them in good faith.”

Konashenkov’s distracting creation and dismissal of a conflict between US freedom of navigation and Russian overflight rights is misguided for a number of reasons. First, consistent with the principle of lex specialis, INCSEA is the relevant starting point to discuss the two recent incidents. INCSEA creates specific legal obligations for US and Russian naval and associated forces on the high seas. Vague invocations of freedom of navigation on the high seas and in international airspace are overridden in favor of the more specific law which Russia and the US have agreed will govern these types of interactions.

But more obviously, and readily apparent in the footage of the Cook incident, the conflict that Konashekov is attempting to create between US and Russian freedom of navigation and overflight rights is a false one. The concerted pattern of harassment of the Cook is not an example of the freedom of overflight protected under the law of the sea. The video shows it was not what Russia described as “planned training flights above the neutral waters of the Baltic Sea,” in which, as if coincidentally, “the route of the Russian aircraft crossed the area where the USS Donald Cook was.” Instead, it was intentional interference with a ship enjoying freedom of navigation in international waters. The failure of the Russian aircraft to respond to attempts by the American crew to communicate with them represents bad faith.

Bad faith and denials of international law violations are, unfortunately, a not uncommon occurrence in international relations. But for Putin’s Russia, they are part of a larger strategy of information warfare — what Russia refers to as “reflexive control” — shaping the narrative of events to influence international perceptions. Given the Cook incident was caught on video, Russia’s mischaracterization presents a particularly bold-faced attempt to downplay its provocativeness and to sow confusion. Recent events are the latest in a string of antagonistic acts by Russian aircraft against US personnel operating in international waters and airspace, in which Russia has pushed the boundaries of INCSEA. These include a 2014 flyby of the Cook in the Black Sea, a June 2015 incident in which Russia falsely claimed its aircraft had forced the USS Ross to change course, and an October 2015 incident off the Korean peninsula, in which Russian planes approached the USS Ronald Reagan while it participated in a training exercise

International Law Matters

Will Russian pilots become less antagonistic if the US emphasizes that their actions violated international law? It can’t hurt to make the argument. To quote Churchill, “it is always better to jaw-jaw than to war-war.” But there is much additional practical value in highlighting Russia’s behavior as a violation of international standards.

Violation by one state of a treaty obligation allows the ‘injured party’ to lawfully take countermeasures. Any such countermeasures should be proportional and designed to induce compliance with the treaty by the breaching state, consistent with Articles 51 and 49 of the Draft Articles on State Responsibility for Internationally Wrongful Acts. Of course, to be proportional, countermeasures need not be equivalent. With a military that prides itself on professionalism and personnel safety, the US is unlikely to start authorizing its aircraft to buzz Russian ships. But in a globalized world in which states cooperate on a range of issues, there is room for a measured response that would promote Russian compliance with INCSEA. If any countermeasure requires the acquiescence of a third state in order to be effective, it will be helpful to establish that it is lawful as a response to a breach by Russia of its INCSEA obligations.

Drawing attention to INCSEA is also an important reminder of the seriousness of the conduct at issue. INCSEA prohibits actions that needlessly risk accidents, miscommunication, and escalation. Events like the flyover of the Cook can easily end in tragedy. INCSEA was negotiated following a series of incidents between the Soviet and American navies in the 1960s. One such incident was the 1968 crash of a Soviet Tu-16 Badger after it conducted several close passes of the USS Essex. That accident resulted in the death of the Soviet bomber’s entire crew. Recently, a Russian aircraft was shot down after approaching Turkish airspace in Syria. While not the type of situation covered by INCSEA, it illustrates how quickly aerial encounters intended to test boundaries can, based on perception of a threat, lead to a use of force.

More generally, it is in the US’s interest to reaffirm to Russia the principle of pacta sunt servanda. The expectation that states adhere to their agreements in good faith is an important pillar of international security. Putin’s Russia has a penchant for selectively and imprecisely alleging violations of international law by other states while failing to uphold its own obligations. Russia has justified its antagonism in Eastern Europe by claiming an increased NATO presence there violates the 1997 Founding Act, an argument that ignores the clear text of the agreement and customary rules on treaty interpretation. Recently, Russia sought to enforce its rights under the Open Skies Treaty to conduct overflight of US territory for reconnaissance, despite its own failure to comply with the treaty. Grounding discussion of recent incidents in international law will signal that Russia may not invoke international legal principles to its benefit while feigning incredulousness and ignoring its obligations at its convenience.

Finally, reaffirming pacta sunt servanda — particularly for a document like INCSEA that governs conduct at sea — is important beyond US-Russia relations. Such agreements — and the norm that their signatories adhere to them in good faith — is crucial at a time when many states are confronting maritime disputes in Asia. This is especially important considering that so far in the Pacific, key agreements have taken the form of non-binding “soft-law.” The 2014 Code for Unplanned Encounters at Sea (CUES), signed by 21 Pacific nations (including Russia and the US) drew inspiration from standards of conduct in INCSEA, though replacing the binding “shalls” with non-binding “shoulds.” While non-binding mechanisms have their limitations, they promote norms which may later harden and lead to binding legal agreements. Many of the reasons that almost all states comply with almost all of their international legal obligations almost all of the time, to paraphrase Louis Henkin, apply to soft-law mechanisms. Ensuring compliance requires that foundational principles like pacta sunt servanda be periodically reaffirmed.

Anchoring interactions between ships and aircraft at sea to legal frameworks is vital to ensure states resolve their differences peacefully and through diplomatic means. Explicit invocations of international law and norms reinforce the expectation of “jaw-jaw” over “war-war.” In this respect, the fact that Russia’s antics in the Baltic appear to have been timed to disrupt the NATO-Russia Council meeting is discouraging. One can only hope that, going forward, Russia appreciates the wisdom of Churchill as much as its leader admires a certain poor impersonator.

The views expressed here are the author’s personal views and do not reflect those of the Department of Defense, the United States Navy, or any other department or agency of the United States Government. The analysis presented here stems from his academic research of publicly available sources, not from protected operational information. Any views expressed are those of the author and not those of the American Society of International Law.