Threats of Force under Article 2(4): From Abstraction to Practice
By Davit Khachatryan
Published on 23 January 2026
Trump’s recent statements on the use of power are striking for their candour. The usual diplomatic language and legal justifications are largely absent. In the aftermath of the illegal use of force in Venezuela, he has again turned to Greenland, reviving the idea that the United States should secure ownership and indicating that different options remain on the table. The underlying message is that the United States’ policy is being articulated in terms of capability and strategic preference.
When a powerful state speaks as if the use of force is routinely available, even casually, it reshapes the space in which other states make decisions. Against this background, the United States now appears content to achieve objectives through the threat of force.
Threats of Force under Article 2(4) of the UN Charter
International law treats threats seriously. It places them on the same normative footing as the most serious breach of the peace: the use of force in international relations. Article 2(4) of the UN Charter prohibits the ‘threat or use of force.’ The ‘or’ matters. A credible threat of force can trigger the right of self-defence under Article 51 in the same way as force itself. Waiting for violence to materialise often means waiting too long (Dinstein pp 233–236; Gray 150–156).
The Venezuela operation, with its projection of power and willingness to act beyond mere positioning, adds real weight to how others perceive American threats. Nevertheless, even a serious threat must point to an attack that is instant, overwhelming, and leaves no moment for deliberation before self-defence would be justified. Anticipatory self-defence applies only where an armed attack is so imminent that waiting would defeat the very right to defend (Dinstein pp 191–194). In the Nuclear Weapons Advisory Opinion, the International Court of Justice stated that notions of ‘threat’ and ‘use’ of force under Article 2(4) stand together in the sense that if the use of force envisaged would be unlawful, then the threat of such force is likewise unlawful. (para. 47). Mere rhetoric, political bravado, or abstract statements of military capacity fall short of unlawful threats. In Nicaragua, the Court treated coercive pressure backed by force as incompatible with the prohibition even without open hostilities (para. 227).
Greenland and Taiwan
Trump’s turn to national security does not resolve the legal difficulty of the Greenland claim. Security, as he frames it, offers no clear limiting principle. Greenland is not presented as an imminent threat, nor as a source of unavoidable danger requiring extraordinary measures. Instead, security is invoked as a justification for permanence and control. From a legal perspective, when security is detached from imminence and necessity, it ceases to explain action and starts to excuse it.
In his interview, Trump was explicit about what he wants. Leasing arrangements and security cooperation do not deliver the objective he describes. He spoke instead about ownership, explaining that ownership offers a level of permanence and decisiveness that negotiated arrangements cannot provide. In that context, coercion enters as the only option left standing once lawful, consent-based avenues are treated as inadequate. Trump makes that implication explicit. He says the United States will get Greenland ‘one way or another,’ whether those involved like it or not. This language materially narrows the space for genuine consent: once consent is treated as optional and resistance as something to be overcome, the use of force no longer appears as a distant contingency. It becomes a foreseeable endpoint of the posture already set in motion.
The appeal to Russia and China completes this move. Trump suggests that if the United States does not act, other major powers will. As a justification, however, this framing does not map neatly onto the Charter’s framework. It shifts responsibility from present legal constraints to speculative future competition. Thus, imminence is treated as prediction, and necessity as strategic anxiety. International law rejects this logic precisely because it has no internal brake. If anticipated rivalry were enough to justify territorial acquisition, the prohibition on force would dissolve into a rule against being too slow.
The point is reinforced by the 1970 Friendly Relations Declaration, which articulates the Charter’s core principles in more operational terms. It affirms that States must refrain from the threat or use of force against the territorial integrity or political independence of any State, and that no territorial acquisition resulting from the threat or use of force shall be recognised as lawful. It also links the prohibition to a broader duty of peaceful settlement and good faith relations, emphasising that disputes must be addressed through lawful means rather than coercion.
Trump claims that if the United States does not take it, Russia or China will. This is a speculative security rationale. If Greenland, as part of the Kingdom of Denmark, were subject to an armed attack, Denmark would be entitled to act in self-defence, and its allies could respond through collective self-defence under Article 51. Moreover, an armed attack against Denmark could engage consultations under Article 4 of the North Atlantic Treaty and, where the threshold is met, collective action under Article 5. In legal terms, the claim that Russia or China might someday threaten Greenland attempts to manufacture a necessity to reach an outcome that the Charter framework prohibits: territorial acquisition through coercion.
Follow the logic for two steps, and the implications become clearer. Canada is, in strategic terms, at least as central to the Arctic picture as Greenland. It sits closer to key routes, closer to Russia, and it forms the land bridge giving the United States access to Alaska. If the premise that a rival might someday seek influence or control and that possibility justifies pre-emptive acquisition, identifying a principled stopping point becomes difficult. Similar reasoning could be extended to Canada as a purported vulnerability, particularly given that ‘51st state‘ rhetoric has circulated in political discourse.
This illustrates the core legal difficulty. A security claim untethered from clear thresholds can be expanded indefinitely, recasting neighbours as risks and borders as provisional. The Charter’s framework is designed to prevent exactly this move from strategic anxiety to coercive outcome. An armed attack may trigger self-defence under Article 51, including collective self-defence. Speculation about future competition does not. Once that distinction is blurred, restraint risks becoming dependent on political discretion rather than legal constraint, which is precisely what Article 2(4) was intended to avoid.
Taiwan pushes this logic even further. When asked whether the United States’ conduct might embolden China to move against it, Trump’s response was strikingly thin in legal terms: it was ‘up to’ Xi Jinping what China does, he said, and he did not expect it to happen while he was president. What is missing from that answer is as important as what is said. There is no acknowledgement that the use of force against Taiwan would be unlawful, regardless of who sits in Beijing or Washington. The framing is deeply destabilising because it shifts the questions from legal constraint to personal expectation. Saying ‘it’s up to him’ concedes unilateral use of force as a tolerable option, both for China and, by implication, for the United States.
This is no longer a case of aggressive rhetoric hovering short of a threat. The combination of security untethered from necessity and an explicit willingness to proceed regardless of consent produces a clear legal signal. The question is no longer whether force has been mentioned, but how real the threat has become in context. A threat of force has not fully crystallised, at least not yet. However, the prospect of coercion becomes increasingly credible as lawful options are treated as inadequate and consent is framed as optional. If this posture continues, crossing into an unlawful threat under Article 2(4) may require little, if any, additional escalation.
Conclusion
The Greenland issue reflects a broader shift in how coercion is articulated in contemporary international relations. Territorial control is increasingly framed as a response to insecurity, with legal constraint treated as contingent rather than constitutive. The risk is that this approach normalises pressure as a substitute for consent, and capability as a substitute for legal entitlement.
The legal line has not yet been crossed in the narrowest sense. Yet under Article 2(4), this is a familiar pathway through which unlawful threats take shape: lawful options are discounted, consent is treated as optional, security is invoked without clear necessity, and coercion remains the implied means of achieving the stated objective. On that basis, the conduct already sits close to the Article 2(4) threshold.
A final point concerns the preventive function of the Charter regime. Threats of force are often discussed in doctrine as difficult to identify in practice, precisely because they rarely take the form of explicit ultimatums. The present context illustrates why the prohibition matters: coercion can operate through language, posture, and the narrowing of lawful alternatives long before force is used.
Davit Khachatryan is an international law expert and lecturer at the American University of Armenia. He specializes in public international law, alternative dispute resolution, investment law, international humanitarian law, and security.