Source: https://www.msuilr.org/msuilr-legalforum-blogs/2018/4/9/the-legality-or-lack-thereof-of-north-korean-nuclear-weapons
Timestamp: 2019-04-19 03:27:15+00:00

Document:
Only the United States, China, United Kingdom, France, and Russia were classified as Nuclear-Weapon States under the NPT, which means that North Korea was barred from acquiring nuclear weapons under any means. Additionally, North and South Korea signed the Joint Declaration of South and North Korea on the Denuclearization of the Korean Peninsula on February 19,1992. Article one of the treaty specifically states, "South and North Korea shall not test, manufacture, produce, receive, possess, store, deploy or use nuclear weapons."
On March 12, 1993 North Korea announced its intention to withdraw from the NPT under art. 10. Parties are allowed "to withdraw from the Treaty if it decides that extraordinary events, related to the subject matter of this Treaty, have jeopardized the supreme interests of its country." However, a nation must give 90 day notice before it can withdraw from the NPT. North Korea gave eighty-nine days of notice but on October 21, 1994 North Korea signed an agreement with the United States, which provided that "[t]he DPRK will remain a party to the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) and will allow implementation of its safeguards agreement under the Treaty."
Despite signing multiple treaties stating it will not acquire nuclear weapons, North Korea withdrew from the NPT on January 10, 2003. North Korea only gave one day of notice, arguing that they had already completed the other 89 days of notice in 1993. At a conference between China, North Korea, and the United States held on April 23, 2003, the North Korean delegate informed the United States delegate that North Korea possessed nuclear weapons.
It is unclear as to whether North Korea properly withdrew from the NPT considering their days of notice were separated by a decade and they did not cite an extraordinary event which jeopardized an extreme interest of the state. However, despite a potential withdrawal from the NPT, North Korea was still bound by its joint declaration not to acquire nuclear weapons. Even if North Korea only considered the joint declaration as a position statement, rather than a treaty, the International Court of Justice has stated, "when it is the intention of the State making the declaration that it should become bound according to its terms, that intention confers on the declaration the character of a legal undertaking, the State being thenceforth legally required to follow a course of conduct consistent with the declaration." When North Korea signed the Joint Declaration they committed a unilateral act which created a legal obligation for them to follow.
Even if North Korea were not barred by any treaty from acquiring nuclear weapons, North Korea is barred from possessing Nuclear Weapons as a member of the United Nations. On October 09, 2006, the United Nations Security Council passed Resolution 1718. Un Security Resolution 1718 demanded that North Korea return to the NPT and further decided that North Korea "shall abandon all nuclear weapons and existing nuclear programs in a complete, verifiable and irreversible manner, shall act strictly in accordance with the obligations applicable to parties under the Treaty on the Non-Proliferation of Nuclear Weapons." Article twenty-five of the United Nations Charter requires all members of the UN to "accept and carry out the decisions of the Security Council." As a member of the United Nations North Korea is required to rejoin the NPT and follow all nuclear disarmament requirements, as directed by resolution 1718.
The UN Security Council acted under chapter seven of the UN Charter when it approved Resolution 1718. Article 39 of Chapter Seven allows the UN Security Council to "determine the existence of any threat to the peace, breach of the peace, or act of aggression" and take appropriate measures to restore international peace. Accordingly, Resolution 1718, acting under article forty-one of the UN Charter, implemented sanctions against North Korea to coerce them into fulfilling their obligations as outlined by Resolution 1718. The United Nations Security Council has subsequently passed eight additional security council resolutions strengthening the sanctions on North Korea.
Finally, North Korea is still bound by the provisions of the NPT, even if they are no longer members, as the NPT has become customary international law. The International Court of Justice considers customary international law binding on all nations, as article 38 states the ICJ shall apply international custom, as evidence of a general practice accepted as law when deciding cases. The International Court of Justice stated in the North Sea Continental Shelf case that "even without the passage of any considerable period of time, a very widespread and representative participation in the convention might suffice of itself [to make customary international law], provided it included that of States whose interests were specially affected." The NPT currently has 191 parties to the treaty. Only South Sudan, India, Pakistan, Israel, and North Korea, who withdrew, are not a party to the NPT. The NPT has been in effect for fifty years and the vast majority of states have become parties to the NPT and upheld its stipulations against obtaining nuclear weapons. Due to the overwhelming participation in the NPT, it is considered customary international law and North Korea must adhere to the requirements of article two which precludes North Korea from obtaining nuclear weapons.
 Treaty on the Non-Proliferation of Nuclear Weapons: Status of the Treaty, United Nations Office for Disarmament Affairs (Jan. 04, 2018), http://disarmament.un.org/treaties/t/npt.
 Treaty on the Non-Proliferation of Nuclear Weapons art. 2., July 01, 1968, 729 U.N.T.S. 10485 [Hereinafter NPT].
 Joint Declaration of South and North Korea on the Denuclearization of the Korean Peninsula, Democratic People's Republic of Korea-Republic of Korea, Feb. 19,1992.
 NPT, supra note 2, art. 10.
 US-DPRK Agreed Framework, art. 4(1), Oct. 21, 1994.
 Chronology of U.S.-North Korean Nuclear and Missile Diplomacy, Arms Control Association (Jan. 07, 2018), https://www.armscontrol.org/factsheets/dprkchron.
 Nuclear Test Case (Australia & New Zealand v. France), Judgment ¶ 43, I.C.J. Reports 1974.
 S.C. Res. 1718, arts. 4, 6 (Oct. 14, 2006).
 Id. art. 41; S.C. Res. 1718, art. 8 (Oct. 14, 2006).
  UN Security Council Resolutions on North Korea, Arms Control Association (Jan. 04, 2018), https://www.armscontrol.org/factsheets/UN-Security-Council-Resolutions-on-North-Korea#res1718.
 Statute of the International Court of Justice art. 38.

References: art. 10
 art. 2
 art. 10
 art. 4
 v. 
 art. 41
 art. 8
 art. 38