By: Marlene Zieah.
Over the years, nations have been trying to devise a way to rule nuclear weapon use as against international law. If their efforts were successful, they may be able to force North Korea to dismantle their nuclear weapons program. However, a major obstacle has been the non-binding nature of most international sources of law. This is because countries that defend their nuclear weapon use usually do so by claiming that they are not acting unlawfully because as unpopular as their actions may be, they are technically not in violation of any established prohibitory international rule/law. Failed attempts, including treaties, customs, general principles of law, and judicial decisions/expert opinions, have made the issue even more challenging for those nations that strive to end nuclear weapon use on a global scale. However, jus cogens, also commonly referred to as preemptory norms, would operate as a workaround for this problem. Preemptory norms are those that are so fundamental, that no source of international law may derogate from them. In other words, jus cogens hold the highest rank on the hierarchy of international sources of law, including treaties. Prohibitions with strong potential for jus cogens status include the prohibition against torture, aggressive use of force, genocide, slavery and slave trade, piracy, racial discrimination, and hostilities directed at civilian populations. The prohibition against nuclear weapon use is significantly similar to these prohibitions, and if it were given international jus cogens status, it would place North Korea and other nuclear weapon states in violation of international law.
For a prohibition to gain jus cogens status, it must meet three criteria: 1.) be grounded in morality; 2.) be fundamental to international order; and 3.) be a widespread international practice that has a sense of obligation among the states (opinio juris). The first and second criterion are mostly subjective, while the third requires more objective evidence. The International Court of Justice (ICJ) performs sort of a jus cogens analysis on the legality of nuclear weapons use, although it does not actually decide on the question. This article will show how a prohibition on nuclear weapon use would satisfy the jus cogens test and why the ICJ’s advisory opinion actually does reach and answer the question.
Establishing a moral basis for a ban on nuclear weapon use is easily accomplished because of their potential for mass destruction. The ICJ identifies various reasons nuclear weapon use is immoral. First, it does not separate innocent people from those directly involved in combat. Second, the effects of radiation can last decades after, causing unlimited health risks for inhabitants. Lastly, nuclear weapons are “largely uncontrollable” by man, creating a risk of total destruction to humanity as a whole.
A ban on nuclear weapons is essential to international order because “general principles . . . in the maintenance of international peace and security, includ[e] the principles governing disarmament[.]” For example, whether or not North Korea decides to maintain nuclear weapons has a direct impact on its relationship with several countries, including China and the United States. The recent threat posed by North Korea’s use of nuclear weapons prompted the United States to respond in a threat of “fire and fury” should they continue. U.S. allies then unanimously imposed sanctions against North Korea, giving rise to tensions that before then, had not existed. Most significantly, the U.S.’s response left China, which currently holds the second-largest economy, in a challenging position. This disagreement among nations forces many of them to have to make difficult choices between actions that are in their individual best interest, and those necessary to protect international order.
The last criterion is more of a two-part test, the former easier to satisfy than the latter, because though a ban on nuclear weapon use is the popular choice among most nations, refusal by other nations makes the prohibition seem optional. In order to be considered a general practice, a prohibition does not have to be unanimous – a majority is sufficient and easily satisfied here. For example, in 2017, one-hundred and twenty-two nations signed The Treaty on the Prohibition of Nuclear Weapons – amounting to over half of all nations. Even more striking is the fact that only nine nations, out of one-hundred and ninety-five, actually have nuclear weapons.
The opinio juris requirement – i.e., a sense of obligation by all nations to follow a widespread international practice – is the second part of the third criterion that was not found by the ICJ. The ICJ reasoned that because some nations have refused to sign treaties banning nuclear weapons, and have made developmental efforts in nuclear weapon production, they must not feel obligated to follow the general practice. However, the ICJ ignores the preemptory nature of a principle with jus cogens status – that is, it does not require a showing of opinio juris as strong and as matter-of-fact as what is required when establishing customary rules of international law. Further, though it did not reach the question, the ICJ made an excellent case for nuclear weapons bans achieving jus cogens status. For example, it referred to the prohibition as “so fundamental to the respect of the human person” that these “rules are to be observed by all States whether or not they have ratified the conventions that contain them, because they constitute intransgressible principles of international customary law” (emphasis added). This statement by the ICJ appears to establish every element of the jus cogens test, softening the opinio juris requirement because the principle behind a ban on nuclear weapons is, by its very nature, obligatory. This is further supported by the fact that in all of international history, nuclear weapons have only been used in combat twice, and that occurred roughly seventy-two years ago.
In sum, North Korea and other nuclear weapons states should be held in violation of international law if they continue to use and produce threats to mankind that disrupt international order and fly in the face of universal practices accepted by all nations for centuries.
 Gro Nystuen and Kjølv Egeland, A ‘Legal Gap’? Nuclear Weapons Under International Law, ARMS CONTROL TODAY (Mar. 2016), https://www.armscontrol.org/ACT/2016_03/Features/A-Legal-Gap-Nuclear-Weapons-Under-International-Law.
 The Effects of Nuclear Weapons under International Law, briefing paper, ARTICLE36 (Dec. 2014), available at http://www.article36.org/wp-content/uploads/2014/12/Nuclear-weapons-under-international-lawbb5.12.14.pdf.
 Id. at n. 52.
 See Vienna Convention on the Law of Treaties, art. 53, May 23, 1969, 1155 U.N.T.S. 332, 344.
 Id. at 347.
 Charles Hyun, The Prohibition of Chemical Weapons: Moving Towards Jus Cogens Status, 88 S. CAL. L. REV 1463, 1465 (2015).
 Id. at 1488-89.
 See Walter Gangl, The Jus Cogens Dimensions of Nuclear Technology, 13 Cornell Int'l. L.J. 63, 64 (1980).
 See Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, 1996 I.C.J. 226 (July 8, 1996).
 Id. at 258, para. 83.
 Id. at 257, para. 79.
 Id. at 248, para. 57.
 Id. at 257, para. 78.
 Id. at 243, para. 35.
 Id. at 262, para. 92.
 Id. at 233, para. 11.
 See Stephen Collinson, Trump's 'Fire and Fury' Rhetoric Met with Defiance by Kim Jong Un, CNN (Sept. 3, 2017) 7:48 PM, http://www.cnn.com/2017/09/03/politics/north-korea-trump-kim-jong-un-rhetoric/index.html.
 Adam Taylor, What the New U.N. Sanctions on North Korea Mean, THE WASHINGTON POST (Aug. 7, 2017), https://www.washingtonpost.com/news/worldviews/wp/2017/08/07/what-the-new-u-n-sanctions-on-north-korea-mean/?utm_term=.7847105a4e20.
 See Gangl, supra note 11, at 75.
 See The Effects of Nuclear Weapons under International Law, supra note 3.
 Gangl, supra note 11, at 76.
 Aria Bendix, 122 Nations Approve 'Historic' Treaty Banning Nuclear Weapons, THE ATLANTIC (Jul. 8, 2017), https://www.theatlantic.com/news/archive/2017/07/122-nations-approve-historic-treaty-to-ban-nuclear-weapons/533046/; see also The Effects of Nuclear Weapons under International Law, supra note 3 (explaining how even before this historic achievement in international humanitarian law, a ban on nuclear weapons appeared in numerous international documents with worldwide application, was incorporated into the domestic law of nearly all nations, and was consistently supported at both national and international conferences).
 See Gangl, supra note 11, at 75-76; see also Vienna Convention on the Law of Treaties, supra note 7, at 254-55, paras. 67, 73.
 See Vienna Convention on the Law of Treaties, supra note 7, at 254-55, paras. 67, 73; see also Stefaan Smis & Kim Van der Borght, The Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons, 27 GA. INT'L & COMPARATIVE L. REV. 345, 374-76 (1999).
 See Gangl, supra note 11, at 76.
 See Legality of the Threat or Use of Nuclear Weapons, supra note 14, at 257-258, paras. 79, 83.
 Id. at 257, para. 79.
 Id.; see also Gangl, supra note 11, at 76.
 See Smis & Borght, supra note 34, at 374.
 See Gangl, supra note 11, at 74-77.