Written by Conrad Johnson ’28

Introduction

On June 26, 2026, Finnish President Alexander Stubb signed into law legislation overturning the country’s ban on nuclear weapons.¹Eduskunnan vastaus hallituksen esitykseen PLM/2026/75, Puolustusministeriö (June 26, 2026), https://valtioneuvosto.fi/paatokset/paatos?decisionId=6736 (on file with American University International Law Review). Government Proposal HE 72/2026 amended the Nuclear Energy Act and the Criminal Code to allow the import, transport, supply, or possession of nuclear weapons into Finland.²Id.; Finnish Government proposes to amend Nuclear Energy Act and Criminal Code to strengthen NATO’s deterrence and defence, Ministry of Defence (May 3, 2026), https://valtioneuvosto.fi/en/-/236553176/finnish-government-proposes-to-amend-nuclear-energy-act-and-criminal-code-to-strengthen-nato-s-deterrence-and-defence (on file with American University International Law Review). The Finnish government states that the purpose of the law is to eliminate barriers obstructing its participation in the North Atlantic Treaty Organization (NATO), improve national security, and strengthen deterrence.³Press Release, Parliament approved amendments to the Nuclear Energy Act and the Criminal Code, Parliament of Fin. (June 18, 2026) [hereinafter Parliament approved amendments], https://www.parliament.fi/en/press-releases/parliament-approved-amendments-to-the-nuclear-energy-act-and-the-criminal-code (on file with American University International Law Review). Finland’s repeal of its nuclear weapons ban arrives at a time when the country is further integrating itself into NATO following Russia’s invasion of Ukraine, and the United States is considering expanding its nuclear umbrella into Eastern Europe.⁴Relations with Finland, NATO (Oct. 3, 2024), https://www.nato.int/en/what-we-do/partnerships-and-cooperation/relations-with-finland (on file with American University International Law Review); Linus Höller, US may consider placing nukes in Poland, Baltic States, report says, Defense News (June 2, 2026), https://www.defensenews.com/global/europe/2026/06/02/us-may-consider-placing-nukes-in-poland-baltic-states-report-says/ (on file with American University International Law Review).

This law would permit Finland to participate in NATO’s nuclear weapons sharing program as its stated purpose is to “remove legal barriers concerning nuclear devices to enable Finland’s homeland defence as part of the Alliance . . . .”⁵Parliament approved amendments, supra note 3. While appearing to contradict the country’s commitments under the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), NATO weapons placed in Finland as a result of this law would not constitute a change of “control” or a “transfer” under Article II of the NPT.

Background

The NPT prohibits nuclear-weapon state parties, like the U.S., from transferring nuclear weapons or control of such weapons to non-nuclear-weapon state parties, like Finland.⁶Treaty on the Non-Proliferation of Nuclear Weapons art. 1, July 1, 1968, 21 U.S.T. 483, 729 U.N.T.S. 161 [hereinafter NPT]. Correspondingly, the NPT prohibits non-nuclear-weapon state parties from receiving nuclear weapons or exercising control over such weapons from nuclear-weapon state parties.⁷Id. art. 2.

The NPT was the product of the United Nations Eighteen Nation Committee on Disarmament (ENDC) which met in Geneva, Switzerland from 1965 to 1968 to consider nuclear disarmament policies amid growing anti-nuclear weapons sentiment.⁸Tapio Juntunen, Finland: From Curious Observer to Active Accommodator of the NPT Process, in Neutral Eur. and the Creation of the Nonproliferation Regime 130, 136 (Pascal Lottaz & Yoko Iwama eds., 2024); see id. at 43–45. Article I of the treaty prohibits the “transfer” of nuclear weapons from nuclear-weapon states to the “control” of non-nuclear-weapon states.⁹NPT, supra note 6, art. 1. Similarly, Article II obligates non-nuclear-weapons states to not receive the “transfer” or “control” of nuclear weapons from nuclear-weapons states.¹⁰Id. art. 2. However, these terms are not defined in the treaty text.¹¹See generally id. art. 1–3 (excluding definitions of “transfer” and “control”).The treaty also limits nuclear-weapons states to the U.S., the United Kingdom, the Soviet Union, France, and China.¹²See id. art. 9, para. 3 (defining a nuclear-weapons state as a state that “manufactured and exploded a nuclear weapon or other nuclear explosive device prior to 1 January, 1967”, a criterion met only by the United States, the United Kingdom, the Soviet Union, France, and China).

Finland is a party to the NPT, which it ratified in 1969.¹³Finland an Active Promoter of the NPT, Ministry for Foreign Affs. of Fin. (May 6, 2015), https://um.fi/current-affairs/-/asset_publisher/gc654PySnjTX/content/finland-an-active-promoter-of-the-npt (on file with American University International Law Review). It was the first country to sign the treaty and played a significant role in its creation.¹⁴Juntunen, supra note 8, at 132. Despite its observer status at the ENDC, Finland chaired the effort in the United Nations General Assembly to obtain treaty signatures.¹⁵Id.

Legal Analysis

Finland’s participation in NATO’s nuclear weapons sharing program would not constitute a transfer of nuclear weapons from the U.S. as defined in the NPT, nor result in Finland’s ability to exercise control over them.¹⁶See Evans Gerakas, David S. Patterson & Carolyn B. Yee, Foreign Relations of the United States, 1964–1968, Volume XI, Arms Control and Disarmament 576 (David S. Patterson ed., 1997) (stating that U.S. nuclear weapon deployments do not constitute a transfer or loss of control).

Under the program’s structure, no transfer occurs because only the nuclear-weapons state is permitted to maintain, access, and secure the weapons.¹⁷NATO, NATO and Nuclear Non-Proliferation and Disarmament (July 9, 2024) https://www.nato.int/content/dam/nato/legacy-wcm/media_pdf/2024/7/pdf/240709-Nuclear-Non-Proliferation_Disarmament_en.pdf (on file with American University International Law Review).Moreover, forward-deployed American nuclear weapons remain under the operational control of the U.S., though physically located in another country.¹⁸Anthony J. Colangelo, The Legality of Nuclear-Weapons Sharing Arrangements Under International Law: United States-NATO and Russia-Belarus, 61 Stan. J. Int’l L. 1, 159 (2025) (quoting Hayashi’s explanation of how NATO nuclear sharing arrangements operate in practice).  Accordingly, only the U.S. would possess the ability to launch nuclear weapons from inside Finland.¹⁹See NATO, supra note 17 (stating that “the United States retains full custody and control over its nuclear weapons forward deployed in Europe”). Therefore, hosting American weapons would neither constitute a “transfer” nor an abdication of “control” if Finland were to participate.²⁰See Gerakas, Patterson & Yee, supra note 16, at 576 (stating that U.S. nuclear weapon deployments do not constitute a transfer or loss of control).

However, the program operates on a system where the host country can refuse the launching of nuclear weapons from its territory.²¹Mika Hayashi, NATO’s Nuclear Sharing Arrangements Revisited in Light of the NPT and the TPNW, 26 J. Conflict & Sec. L. 471, 473–74 (2021). For example, the U.S. would be unable to launch its nuclear bombs located at Büchel Air Base in Germany if the German government objected to their use.²²See Colangelo, supra note 18, at 159 (describing a hypothetical based on Hayashi’s analysis whereby host states can veto U.S. nuclear launches). This constitutes an effective veto from the host country.²³Id.

Conclusion

Finland’s repeal of its nuclear weapons ban reflects its rapid shift from neutrality to alignment with NATO and Western Europe.²⁴Amelia Nierenberg & Johanna Lemola, Finland Lifts a Nuclear Weapons Ban, Eyeing an Uncertain World, N.Y. Times (Jun. 17, 2026), https://www.nytimes.com/2026/06/17/world/europe/finland-nuclear-devices.html (on file with American University International Law Review). Finland has historically been careful of provoking Russia, its neighbor, often pursuing neutrality to prevent tension.²⁵Juntunen, supra note 8, at 131–32. However, this law, coupled with Finland’s accession to NATO following Russia’s invasion of Ukraine, suggests that the Finnish government no longer believes that neutrality is enough to prevent Russian aggression.²⁶Phelan Chatterjee, How Sweden and Finland went from neutral to Nato, BBC (July 11, 2023), https://www.bbc.com/news/world-europe-61397478 (on file with American University International Law Review); see Nierenberg & Lemola, supra note 24 (highlighting Finland’s shift from geopolitical caution with Russia to aligning its nuclear laws with other NATO states).