The Legality of North Korea’s Threats to Use of Force

By Guest Contributor Maitreyee Dixit

As Trump and Kim Jong-Un exchange threats over Twitter, television, and speeches in the UN General Assembly, one cannot help but wonder whether such threats, especially North Korea’s, are legally permissible.

Does international law permit threats to use force, especially the likes being exchanged between two States armed with nuclear weapons? Article 2(4) of the United Nations Charter, in fact, prohibits not only the use of force but the threat to use of force, which has been not dealt with as extensively as the use of force itself in scholarship.

Even jurisprudence on this subject is sparse, with the International Court of Justice (ICJ) adjudicating upon it only in the Nuclear Weapons advisory opinion and the Nicaragua case. The Permanent Court of Arbitration has held the threat to use of force to be a violation of Article 2(4) of the United Nations Charter in Guyana/Suriname matter.

It was held in Nicaragua that the level of armament of a nation is its sovereign prerogative, and in the absence of international obligations regulating the same, cannot constitute a threat under Article 2(4); however, this position was altered in the Nuclear Weapons case, which considered the possibility of such a nuclear armament being a threat, even though in limited sense. The Court laid down-

Some States put forward the argument that possession of nuclear weapons is itself an unlawful threat to use force. Possession of nuclear weapons may indeed justify an inference of preparedness to use them…Whether this (possession of nuclear weapons) is a ‘threat’ contrary to Article 2, paragraph 4, depends upon whether the particular use of force envisaged would be directed against the territorial integrity or political independence of a State, or against the Purposes of the United Nations or whether, in the event that it were intended as a means of defense, it would necessarily violate the principles of necessity and proportionality. In any of these circumstances the use of force, and the threat to use it, would be unlawful under the law of the Charter.”

This would entail that the possession of nuclear weapons itself would be a threat falling under the prohibition imposed by Article 2(4) of the Charter, if the use of those weapons is envisaged against the pointers enumerated by the Court.

In scholarship, there has been a divergence of opinion with respect to what constitutes a threat of use of force which violates Article 2(4). While scholars like Romana Sadurska define the restriction permissively, considering the threat of use of force to be a better alternative than the actual use of force in diplomatic relations; the others are wary of the risks of such a definition. Amongst the second group, the most cited theorization is that of Brownlie, which was also adopted by the ICJ in the Nuclear Weapons opinion. Brownlie defines an illegal threat to use of force as “an express or implied promise by a State of a resort to force conditional on non-acceptance of certain demands of that State”.

He further asserts that there exists symmetry between the legality of the threat of use of force and the actual use of force. In essence, if the use of force in a circumstance is considered unlawful, then the threat of use of such force cannot be considered lawful. Thus, the two exceptions to the prohibition of threats to use of force will also be self-defense and force sanctioned by the United Nations Security Council (UNSC), corresponding to the exceptions of the actual use of force.

Authors like Roscini theorize these threats differently, inasmuch as they do not consider demands made by the threatening State necessary for the threats to be illegal. Hence, even if there exists no specific demand made of the targeted state, the threat may still reach the threshold of an illegal threat. Roscini uses the ‘will’ of the threatening state as the defining factor of the illegal threat, meaning that the actual use of force is based upon the ‘will’ of the responsible State. Any threat that fulfills that requirement then becomes an illegal threat, regardless of whether force follows it.

Furthermore, according to Roscini, it is not required to prove that one particular statement, in isolation, amounts to a threat of use of force to invoke Article 2(4). To the contrary, the relationship between the concerned states and the context play a key role in determining whether such a ‘threat’ exists. An example of this is the Corfu Channel Case, in which UK’s minesweeping was not seen as a ‘threat’ of use of force, in the specific context of a previous firing by Albania.

It is in this framework that the threats of North Korea (NK) have to be analyzed as a violation of Article 2(4).

  1. The 2013 Threats

Threats and hostile communication being exchanged between the U.S. and NK is no recent development, deteriorating further with NK testing nuclear weapons under King Jong-Il and the acceleration of its nuclear program.

NK had threatened the U.S. with nuclear strikes as far back as 2013, which was triggered by the latter’s practice-bombing exercise over the Korean peninsula in the wake of escalating tensions between South Korea (SK) and NK. There were several threats released by NK, followed by the official release of a picture of Kim Jong-Un “discussing” with his generals “plans to strike the mainland U.S.”, Guam, and South Korea, succeeded by statements declaring the ‘readiness’ of its missiles to strike ‘anytime’. It is pertinent to note that all this was taking place in violation of numerous UN sanctions that prohibited the launch of ballistic missiles by NK. Practice drills with drones, cutting off of military hotlines, threats of a pre-emptive nuclear strike characterized NK’s interactions with the U.S. in 2013, similar to the 2017 exchange. However, there is one crucial difference: NK’s increased capability to actually use the threatened nuclear force in the present.

In 2013, there was an uncertainty regarding NK’s capability to build and launch long-range Intercontinental Ballistic Missiles (ICBMs) which could carry nuclear warheads. However, with the number of tests conducted by North Korea this year, accompanied by actual displays of such capacity, such a conclusion can no longer be drawn as comfortably.

2. Response to UNSC Sanctions in August 2017.

The 2017 exchanges have been more hostile and worrisome, with Trump using vitriol to stir tensions further. The adoption of a fresh round of UN sanctions against NK in August, with the U.S. at the helm, triggered a strong reaction from NK. Calling these sanctions a violation of its “sovereignty”, it threatened the U.S. with retaliatory ‘righteous’ action, to which Trump responded with his infamous ‘fire and fury’ remark.

In retaliation, NK released statements threatening to attack Guam with missiles, which were supplemented by NK’s official statements regarding the concretization of a military plan to strike Guam.

3. Missile Launches Over Japan

NK’s successive launches of Ballistic Missiles over Japan marked a turning point in NK-U.S relations, as Japan was cooperating with the U.S. over NK’s nuclear policy and is its ally. Apart from this, the missiles also threatened the U.S. territory in a more direct way: the distance the second missile covered was comparable to that between NK and Guam, and in both cases, the Missiles were launched in Guam’s direction

4. Testing of the Hydrogen Bomb

Between the two launches, NK tested a hydrogen bomb in early September (its sixth nuclear test) which resulted in a 6.3 magnitude tremor. This bomb was said to be eight times more powerful than the bombs dropped by the U.S. on Hiroshima and Nagasaki in the Second World War. Accompanying the ‘test’ was a picture of Kim Jong-Un inspecting a thermonuclear bomb, which led to a detailed reconsideration of NK’s nuclear weapon manufacturing capabilities. This act was firmly condemned by several states across the globe, including Russia and China as it posed a considerable threat to the nuclear non-proliferation agenda.

The conduct of NK necessitated successive UN meetings, which resulted in new sanctions being slapped on NK. NK, in response, threatened to sink Japan and reduce the US to “ashes and darkness”, which was succeeded by the second Missile launch over Hokkaido.

5. Responses to Trump’s speech at the United Nations General Assembly

Trump’s speech in the UNGA, triggered an ‘unprecedented’ response from NK, with Kim Jong-Un himself threatening Trump and U.S. (unlike the usual method: release of reports by the NK agencies), in which he vowed to “surely and definitely tame the mentally deranged U.S. dotard (Trump) with fire.”

NK then threatened to test a hydrogen bomb over the Pacific Ocean in retaliation to Trump’s speech, which would directly affect the U.S. and Japan.

Ri Yong-Ho, NK’s Foreign Minister then gave his speech at the UNGA, claiming that “firing its rockets at the US mainland was inevitable” in the wake of Trump’s responses.

6. Response to Trump’s Tweet on 24th September

Trump responded to Yong-Ho’s speech via Twitter, stating that they (the regime) “won’t be around much longer”. Yong-Ho construed this as a ‘declaration of war’ by the U.S. on NK, which prompted ‘all options’ to be put on the table.

The U.S. has called this “absurd”, and has maintained that their aim is to accomplish peaceful denuclearization of the Korean Peninsula, and not ‘declare war’; which in spite of Trump’s bellicose language, is evident from the U.S.’ continuous efforts at the UNSC.

Yong-Ho further claimed that the ‘declaration’ allowed NK to ‘make countermeasures’ which would include shooting down U.S. strategic bombers which are not even in its airspace. It has, in fact, boosted defenses on its east coast to achieve that objective. The White House has maintained that such an act will contravene international law.


All these facts, when taken cumulatively, fulfill the requirements of an illegal threat according to Brownlie’s and Roscini’s definitions. NK has, through its conduct, promised to use force on the U.S. and its allies, demanding the U.S. and the international community cease its non-proliferation efforts in the Korean region. The threat also fulfills the ‘will’ criterion laid down by Roscini, since the use of nuclear force depends solely on the will of Kim Jong-Un, which has been demonstrated repeatedly.

Employing the opinion in the Nuclear Weapons case, it may be argued that nuclear armament by NK itself may amount to a threat under Article 2(4), as it is not in doubt that if NK does use force, which it has threatened to do against the U.S., Guam, Japan and South Korea, it will violate their territorial integrity. Use of nuclear force can also arguably violate the purpose of the U.N., which is maintaining global peace and security.




The analysis of NK’s threats in the provided framework makes it difficult to deny that that its threats contravene Article 2(4). North Korea’s statements and actions, like conducting missile launches over the territory of Japan, testing hydrogen bombs etcetera, all in violation of UNSC sanctions have the effect of cumulatively fulfilling the criteria laid down for the determination of illegal threats.


One counter argument, however, is crucial to be addressed, albeit in brief. The exchange between NK and Trump has been bilateral, with both sides using fiery rhetoric; in that scenario, shouldn’t NK’s remarks have the benefit of being seen as self defense?


It is indeed possible to envisage counter threats as a measure of self defense when faced with threats of use of force. However, such application cannot be seen as a simple exercise and will largely depend on the choice of a reference point. For example, in the current situation, North Korea’s threats and conduct in and prior to 2013, in the absence of threats by the U.S., make it difficult for them to claim self defense in 2017. The U.S. can claim self defense more effectively in that context. However, keeping in mind Trump’s equally bellicose rhetoric (the threat to “completely destroy NK”) the extent of this permissibility is yet to be examined.


In addition to this, it can be argued that U.S.’ threats have always tried to ensure that NK complies with UNSC sanctions and hence are legal. This too, however, is not rid of complexities. On one hand, U.S.’ threats can be seen to be compatible with the purpose of the United Nations (maintaining global peace and security through nuclear disarmament) and its recourse to UNSC instead of other methods does correspond with peaceful settlement of disputes to a reasonable degree; but on the other hand, legality requires that the very UNSC sanction allows for use of force to ensure compliance for the threats to be legal- like in the case of the Iraqi invasion of Kuwait- which is absent here. It can be argued that this is a narrow construction of the exception, but a broadening of such an exception has to be done cautiously.