Threats of Force and Attribution: The Case of Incoming Heads of State

[Martin Faix is Vice-Dean for International Affairs and Head of the Centre for International Humanitarian and Operational Law, Faculty of Law Palacký University in Olomouc.

Marko Svicevic is a researcher and lecturer at the Centre for International Humanitarian and Operational Law, Faculty of Law, Palacký University in Olomouc and senior research associate at the South African Research Chair in International Law, University of Johannesburg.]

President Donald Trump’s recent comments suggesting the potential annexation of Greenland and the Panama Canal have understandably drawn widespread criticism. While threats of force are not uncommon, it is particularly noteworthy given they were made prior to his inauguration and in his position as the incoming president.  They no doubt raise legitimate questions concerning their implications under international law. Marko Milanovic for example has already addressed questions concerning coercion and the non-intervention rule. Similarly, Ekaterina Antsygina has considered Denmark’s sovereignty over Greenland and the Greenlandic people’s right to self-determination in light of President Trump’s statements about the uncertainty of Denmark’s right over Greenland. Another question which arises is whether such statements ought to be considered a threat of force prohibited under Article 2(4) of the UN Charter. This post considers the question from two perspectives. First, whether the then President-elect’s statements can at all be considered a ‘threat’ of force for purposes of Article 2(4). And second, whether statements made by an incoming president, although not yet in office but who will with relative certainty assume such office, can at all be attributable to a State.

During a press conference on January 7, then President-elect Trump responded to a question asking whether he would rule out the use of military force to acquire Greenland and the Panama Canal. Trump’s response in part was ‘no’, adding that ‘I’m not going to commit to that now’. It should also be mentioned that a follow up question specifically asked of President Trump whether he had ‘directed his staff to take specific action to draw plans’ concerning his refusal to rule out military force. Trump’s response was that his incoming administration was ‘not at that stage’, suggesting that he had not yet entered office to make such decisions. While it is trite that Heads of State formally representing it in international matters may incur responsibility for their statements and conduct, the issue at hand was that such statements were made by an incoming president. Nevertheless, while not officially representing the State, such statements may indeed be reflective of national policy once an incoming president assumes office. 

‘Threats’ of Force Under Article 2(4)

A preliminary question which needs assessment is whether such statements amount to a ‘threat’ of force. Putting aside for the moment the question of attribution, it should be noted that ‘threats’ of force take a variety of forms. As Agata Kleczkowska (p. 16-17) aptly points out, threats may be direct or indirect, oral or written. Consequently, threats may take the form of statements made by State representatives, government representatives’ statements quoted in written press or in government documents, ultimatums, military manoeuvres and military build-ups (Kleczkowska, p. 64 ff; Sadurska, p. 243; Grimal, p. 41 ff). Nevertheless, the fact that such actions or statements may be perceived as threatening is not determinative. 

For a threat to be considered as such under Article 2(4), scholars point to a number of criteria. For one, the statements or conduct in question must in fact relate to ‘force’ (thereby excluding President Trump’s threats of economic coercion against both Canada and Greenland). Such statements or conduct conveying the threat must also be credible. In other words, the State making the threat must have the capacity to follow through with it (p. 60). Taken further, ‘specificity, proximity, and directness’ are important in determining credibility and ultimately whether the threatening State ‘appears rational’, ‘displays sufficient commitment’ to implement the threat, or has a history of following through with its threats (Tams, p. 346, Corten, p. 124). Finally, the threat of force is unlawful where the consequent use of force is itself unlawful (Nuclear Weapons Advisory Opinion, p. 246). Scholars have also addressed the subjective element of threats; considering both the intention of the threatening State and the perception of the State so threatened (Kleczkowska, p. 18-19; Sadurska, p. 241-242, 244-245). Yet, neither of these would seem to be entirely definitive.

Considering Trump’s comments, it is first and foremost clear that such statements, in particular the reference to Greenland and Panama, refer to military force. One could even frame his comments as an ultimatum whereby force is threatened if the territory of Greenland were not handed over to the United States. This would have a number of consequences under international law, including that any subsequent treaty involving the sale or transfer of Greenland to the United States could be considered void (Art. 51, VCLT). This may indeed become relevant in due course considering that one day after President Trump’s remarks, a Congressional bill was introduced concerning the re-purchase of the Panama Canal. 

Even though we may be dealing with ‘force’, the question of credibility of the threat remains ‘central’ (p. 346). Whether President Trump’s comments are entirely credible remains unclear. Ascertaining credibility in the current context exposes an inherent point of criticism; credibility is heavily dependent on perception. On the one hand, the United States certainly has the (military) capacity to carry out threats. It has done so in the past. One need only recall former President Bush’s warnings to Iraq of severe consequences should it fail to comply with UN Security Council resolutions. Those threats were eventually followed up with when it launched Operation Iraqi Freedom. At the same time, these threats were made in the context of the United States ‘War on Terror’ – a different context to the alleged acquisition of territory President Trump refers to. If one considers (as Tams points out) the ‘specificity, proximity, and directness’ as relevant factors in determining credibility, it is worth noting that Trump’s statements might amount to more than just ‘vague’ or ‘uncertain’ threats (or as Corten, p. 115 refers to it, threats which are ‘clearly established’). In this regard, Trump’s comments may be viewed in a more serious light. They are specific in so far as the target of the threat is clearly identifiable, and so too is the desired outcome (the acquisition of a defined territory – Greenland). In addition, whichever way one may view the question of proximity, it is significant that his comments were made mere days before he would assume office as President. 

On the other hand, it has been well pointed out that President Trump occasionally makes statements that are more politically motivated rather than based on actionable strategy (see also Corten’s assertion at p. 124 on Trump’s previous tweets on North Korea and Iran). It is open to question therefore whether the weight attributed to the credibility of a threat ought to sit with the capacity/office of the State making the alleged threat or the person holding that office. One analogy here illustrates this point. Had these comments been made by former President Barack Obama as the incoming President, the situation would likely be viewed in a far more serious light. Consequently, the threat of force would be perceived with far higher credibly.

For their part, neither Panama nor Denmark seemed to have considered his statements as ‘threats’. Danish Prime Minister Mette Frederiksen appeared to have brushed off the comments, suggesting such a scenario would be unimaginable. Similarly, Panama’s response, other than a pushback that the Canal would remain within its sovereignty, has not explicitly framed President Trump’s comments as a threat. The reaction of third States, in particular that of Germany and France warning against any attempt to ‘move borders by force’, suggests that they view these statements with serious political repercussions rather than representing credible threats of force. 

The situation may have been viewed differently if, for example, Denmark (a founding NATO Member) had called for Article 4 consultations under the NATO treaty framework. Likewise, neither Denmark nor Panama, both UN Security Council non-permanent Members, brought the situation to its attention. This is indicative that at most, President Trump’s comments were viewed as political statements rather than threats within the meaning of Article 2(4). It is also worth noting that on 21 January, Panama referred the matter in part to the UN Security Council, exclusively citing however comments made by President Trump to take back the canal during his inauguration speech. Nevertheless, it is interesting that Panama made no mention of President Trump’s comments prior to his inauguration – suggesting it may not have viewed these comments as threats at the time they were made.

In so far as the threat of force is unlawful if it’s actually use would be, it is particularly noteworthy that President Trump’s comments suggest annexation of territory – which would represent one of the clearest unlawful uses of force. Despite his suggestions that the territory in question would be required for national security purposes, the prohibition of annexation is a well-established rule which not even traditional exceptions such as self-defence make provision for.

The Attributability of Statements and Conduct of Incoming Presidents?

Even if one were to conclude that President Trump’s comments do amount to a ‘threat’ of force, a second question is whether such threats are at all attributable to the United States. After all, the prohibition of the threat and use of force in Article 2(4) is one first and foremost between States in their ‘international relations’. 

It is entirely questionable whether the statements or conduct of an incoming President meet the requirements of attribution laid down in the Articles on Responsibility of States for Internationally Wrongful Acts (ARSIWA). The general rule is that the conduct of any organ of State is considered an act of that State under international law (whether legislative, executive, judicial, or any other function regardless of the position – Art. 4(1)). An organ of State includes any person or entity which has such status according to the internal law of that State (Art. 4(2)).

Until 20 January 2025, President Trump exercised no legal authority under United States national law. While under the Presidential Transition Act of 1963 the ‘apparent successful candidate’ may be provided resources to ensure a smooth transition, they are only conferred legal authority after inauguration. Therefore, neither the statements nor conduct of an incoming president represent the conduct of an organ of State (such conduct – and any corresponding capacity – remaining exclusively in the hands of the sitting president). On this basis, it can also not be said that an incoming president exercises ‘governmental authority’ for purposes of Article 5.

In this regard, Article 11 of ARSIWA is also worth noting. Conduct not ordinarily attributable to a State may nevertheless be an act of the State under international law where the State acknowledges and adopts the conduct in question. It is worth noting that the outgoing United States Secretary of State explicitly rejected Trump’s comments. The United States therefore never acknowledged or adopted President Trump’s position. The statements by President Trump before his inauguration therefore cannot be seen to represent the United States in any way, at least not under the rules of attribution.

Such a conclusion is also supported by the wider understanding in international law where the conduct of States concern. The Guiding Principles Applicable to Unilateral Declarations of States, for example, explicitly states that unilateral declarations bind the State ‘only if it is made by an authority vested with the power to do so’ (Art. 4). Similarly and where treaty law concerns, the Vienna Convention on the Law of Treaties expressly stipulates that a person is considered as representing the State if they produce the appropriate powers or if it appears from the practice of the State that they so represent it (Art. 7(1)). Only a limited number of persons, by virtue of their functions, may represent the State without producing full powers. These include Heads of State, Heads of Government, and Ministers for Foreign Affairs (Art. 7(2)(a)). 

That an incoming president does not (yet) formally represent the State and whose statements or conduct do not constitute conduct of an organ of the State would also hamper the very threat they allegedly make. Given the lack of legal authority to represent or bind the State, it is entirely questionable whether an incoming Head of State who threatens another State can at all issue a threat which could be considered credible. After all, as Tams points out, the credibility of a threat is central in order to engage Article 2(4) (p. 346). While it is true that statements of incoming presidents may reflect future national and foreign policy, any alleged threat issued lacks credibility given it is (for the time being) entirely unactionable. For example, while an incoming president may threaten annexation, they cannot order military manoeuvres or exercises in preparation to carry out such actions (thereby giving the alleged threat credibility). Such competences remain fully with the sitting president and their administration.

The case of then President-elect Trump’s statements highlights the complexities of assessing threats of force and attribution in international law. While such comments may reflect future policy directions, they fall short of constituting credible threats reflecting State conduct. This underscores the importance of grounding international law in both legal frameworks and pragmatic assessments of political rhetoric.