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The Application of Economic Pressure to North Korea at Sea: Blockade or Quarantine?

Disclaimer: The views expressed herein are those of the author and are not to be construed as official or reflecting the views of the Commandant or of the U.S. Coast Guard.

By: Daniel Wiltshire

North Korea has made rapid progress in developing an intercontinental ballistic missile (ICBM) with the stated goal of being able to strike the U.S. In turn, multiple nations have applied increasing pressure to dissuade North Korea from obtaining nuclear ICBMs. The U.S. has frozen financial assets and limit illicit financing opportunities. However, North Korea remains steadfast in its quest to achieve nuclear-armed ICBMs. Sanctions have had an impact, but not all nations adequately enforce the sanctions regime, and North Korea has been caught transferring shipments of illicit cargo at sea in violation of sanctions with the assistance of nations like Russia and China.

Some commentators have suggested a naval blockade as an option to ratchet up the effect of and ensure compliance with existing sanctions. Such an action would involve physically intercepting vessels at sea to enforce sanctions, preventing raw materials from entering North Korea, and preventing North Korea from exporting coal. The U.S. Navy has the capability to achieve a blockade of North Korea, but would such an action be legal?

Blockades are legal, per se, as a matter of customary international law, and are permissible under the U.N. Charter. Pursuant to Article 42 of the Charter, blockades may be ordered by the Security Council to maintain or restore international peace and security. However, blockades are considered a use of force and nations may only impose them as a matter of self-defense under Article 51 (see Report of the Secretary-General’s Panel of Inquiry on the 31 May 2010 Flotilla Incident, paragraph 164). The permissible manner for conducting a blockade is further discussed in the San Remo Manual on International Law Applicable to Armed Conflicts at Sea, which addresses international law pertaining to conflicts at sea. Recent examples of lawful blockades legal include the Israeli blockade of Gaza (deemed legal by a U.N. panel) and the blockade of Libya passed by the Security Council in 2011.

While blockades are legal in some circumstances, the question remains whether a blockade of North Korea is permissible under the circumstances that currently exist. Article 93 of the San Remo Manual states that “a blockade shall be declared and notified to all belligerents and neutral States.” Because a blockade occurs between belligerent states, a state of armed conflict in implied to exist. No such state currently exists between the U.S. and North Korea. However, a blockade may also be justified as self-defense. Under Article 51 of the U.N. Charter, a blockade may only be used in response to an armed attack. If a blockade were imposed prevent a possible future attack, such an act would constitute preventive self-defense where a state acts to “. . . prevent some future danger from happening.” As a matter of U.S. doctrine, preventive self-defense has precedent, but the practice is controversial. Consequently, a blockade is a potentially awkward legal tool to apply to North Korea due to the requirement for bellicosity (presupposing a state of armed conflict), and because preventive self-defense is not universally accepted. However, precedent exists for a similar and less bellicose action: a naval quarantine.

During the Cuban Missile Crisis, the United States subjected Cuba to a naval quarantine to prevent the importation of Soviet nuclear weapons. During the crisis, U.S. naval forces intercepted Soviet vessels bound for Cuba. However, the U.S. vessels conducting the inspections did not comprehensively cut off all shipping to Cuba. Rather, they only prevented the entry of vessels carrying offensive weapons. Vessels were only turned back if they contained such weapons; those that did not could proceed. The difference between a broad curtailment of shipping into a country and the targeted prevention of the flow of particular contraband serves as the distinction between a blockade and a quarantine. A quarantine of North Korea has the advantage of being less escalatory than a blockade while being comparatively limited in scope. Additionally, quarantine as a means to prevent nuclear proliferation is supported by on-point precedent, as the U.S. quarantined Cuba specifically to curtail nuclear proliferation.

That said, a quarantine of North Korea has several disadvantages. Unlike a blockade, which is typically general in nature, a quarantine is narrowly targeted toward a specific type or types of cargo. A quarantine could not be expanded in scope and still remain a quarantine. For example, if a quarantine were broadened to include all items prohibited under current economic sanctions (like oil imports, luxury items, etc.), it would cease to be a quarantine and become a blockade. As such, a quarantine of North Korea would likely focus narrowly on nuclear or missile components. This narrow focus would be similar to that of the Proliferation Security Initiative (PSI). Devised in 2003 with North Korea in mind, the PSI allows its 105 participants to interdict shipments of nuclear proliferation material. As such, the PSI is similar to a loose, worldwide quarantine of North Korea. The imposition of a quarantine close to North Korean waters, similar to the quarantine of Cuba, would amount to a more comprehensive or visible means of preventing the spread of nuclear proliferation material. However, in substance, such a quarantine may only amount to a more geographically focused PSI. Furthermore, North Korea’s weapons program is increasingly domestic in nature, meaning that cutting off proliferation materials at sea may no longer be an effective means of curtailing North Korea’s weapons program. Consequently, a quarantine targeted at nuclear proliferation material may be unsuccessful despite the advantage of on-point precedent. However, a quarantine has the advantage of being practically achievable precisely because of the existing PSI. A quarantine limited to the interdiction of materials already prohibited by the PSI could be articulated as rigid enforcement of the now status quo PSI, rather than a new, more escalatory measure.

Ultimately, the political options regarding using naval forces to apply pressure to North Korea are problematic. A blockade is permissible though it assumes a state of armed conflict or preventive self-defense, while a quarantine is permissible and achievable – perhaps as an extension of the PSI – but unlikely to impact North Korean ICBM development if limited to nuclear components. However, blockade and quarantine are both legal options that could be called upon as the crisis of North Korean proliferation moves forward.


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