By Mira Hamad, a teaching and research fellow and a PhD candidate at Université Paris Panthéon-Assas’ Institut des Hautes Études Internationales. Her research focuses on contested areas, territorial and maritime disputes, and dispute resolution.

“son of a w****”, “lunatic” with “small man syndrom”, “toxic masculinity”, “imbecile”, “thief linked to drug trafficking”, “colonialist fascist”, “little rocket man”, “dotard”, “terrorist in a suit”, “dumb***”, “devil”, “you have the charisma of a damp rag”: none of these ad hominem verbal attacks exude courtesy, yet all have been uttered by and against high-ranking State officials in diplomatic contexts.

Before the establishment of the UN Charter, verbal insults between monarchs or heads of state could serve as direct casus belli, provoking armed conflict. For instance, the “fly whisk incident” of 1830 involved the Dey of Algiers verbally insulting and then physically striking the French consul – calling him “a wicked man, an infidel, a traitor” – an affront that France used as a pretext to launch its invasion of Algeria. Similarly, when the Ottoman Sultan Mehmed IV sent an ultimatum demanding their surrender in 1676, the Zaporozhian Cossacks replied with a highly insulting letter mocking the Sultan’s titles and person, calling him a “catamite of Tartary, fool of all the world and underworld, an idiot before God, grandson of the Serpent,” among other crude insults. This provocative reply contributed to escalating conflict between the Cossacks and the Ottoman Empire. These cases illustrate how, in earlier eras of international relations, verbal affronts to sovereign dignity were sometimes sufficient grounds to justify war, reflecting the importance placed on honor and status among rulers. The UN Charter later curtailed such justifications, emphasizing peaceful dispute resolution over personal or verbal insults.

While such language may seem antithetical to current diplomatic norms, it often serves calculated purposes: signaling displeasure, undermining adversaries, and shaping public perception, all without crossing the threshold into open conflict. This phenomenon reflects the complex interplay between diplomacy, domestic politics, and international signaling. Yet it raises a fundamental legal question: are diplomatic insults prohibited under international law? Despite the traditional emphasis on civility, I argue that international law contains no explicit ban on verbal insults exchanged between State officials, leaving this form of symbolic violence largely unregulated.

Insults and Freedom of Expression

International law’s approach to insults is anchored in the broader framework of freedom of expression. Key treaties – including the International Covenant on Civil and Political Rights (ICCPR), the Convention on the Elimination of Racial Discrimination, and the Convention on the Prevention and Punishment of the Crime of Genocide – require states to criminalize speech that incites violence or genocide, but generally do not prohibit speech that is merely offensive or insulting. Article 19 of the ICCPR guarantees the right to hold opinions and to impart information “of all kinds,” subject only to restrictions that are provided by law and necessary for the protection of others’ rights, national security, or public order. Regional courts have reinforced these protections. International treaties such as the Vienna Convention on Diplomatic Relations (1961) and the Convention on Crimes against Internationally Protected Persons (1973) focus on protecting diplomats from physical harm or coercion, not from verbal insults.

The European Court of Human Rights has repeatedly struck down laws that offer special protection to heads of state from insult, emphasizing that public figures must tolerate a higher degree of criticism. In Eon v. France  (insults uttered by a french citizen against the President were described as “criticism through the medium of irreverent satire”) and Otegi Mondragon v. Spain (the criminalisation of insults against the king was deemed “not necessary in a democratic society”), the Court held that criminal penalties for non-violent insults are disproportionate unless justified by a pressing social need. Some states maintain domestic laws penalizing insults to leaders. For example, the polish penal code criminalizes publicly insulting the President as well as foreign heads of state visiting Poland. Similar laws exist in Iceland, Switzerland, and Estonia to name a few (re. Germany, who has since revoked its lèse-majesté law, see here). Human rights organizations have condemned these laws as inconsistent with free speech principles unless they specifically target incitement to violence or hatred. Moreover, the diverse practices of states appear too varied to establish any customary rule of international law (see examples here and here).

Insults as Threats to Use Force

Under international law, insults rarely rise to the level of a prohibited “threat of force.” Article 2(4) of the UN Charter prohibits threats or use of force against the territorial integrity or political independence of states, but this prohibition targets statements or actions implying a promise by one government of a resort to force conditional on non acceptance of its demands. Mere insults, even if provocative or offensive, generally lack the necessary element of coercion or intent to signal likely violence, and “does not in itself amount to use of force” (ICJ, Military and Paramilitary activities, 1986, paras. 227-229). Only when an insult is paired with an explicit or implicit warning of military action – such as a statement threatening armed retaliation – could it potentially be interpreted as a threat of force.

This distinction is critical in diplomatic practice, where verbal sparring can be intense but does not necessarily cross into illegality. For example, the exchange of insults (“little rocket man” and “dotard”) between Donald Trump and Kim Jong-un in 2017–2018 were widely seen as inflammatory but fell short, in themselves, of legal threats under Article 2(4) of the UN Charter. Despite the harsh rhetoric, these insults did not equate military ultimatums, which is the legal threshold for a threat of force. However, it may be argued that Trump’s (disproportionate) vow to “totally destroy” North Korea, in response to “any attack” crossed that threshhold.

Insults and the Obligation to Peacefully Settle Disputes

The UN Charter obligates states to settle disputes peacefully, but this duty is generally understood to address substantive disagreements with the potential to escalate into conflict, not to regulate speech or protect officials’ dignity. While there is an international norm against aggravating disputes, its application to verbal insults is context-dependent and rare.

For an insult to breach the duty of non-aggravation, it must be “intentionally provocative”, and must occur in the context of an ongoing, sensitive dispute and demonstrably worsen tensions or undermine negotiations. What matters here is the perceived purpose of the insult: it should indicate to a reasonable observer that it aims to provoke another State, thereby aggravating an ongoing dispute. Mere offensive rhetoric or undiplomatic language, without clear evidence of aggravating an actual dispute is unlikely to qualify. But even if the threshhold is crossed, it must be said that the duty of non-aggravation has limited practical enforceability, and remains disputed by some, because it’s been considered to be “of so general a nature that a party cannot be entirely clear when contemplating any given action whether or not it falls within its scope”.

Insults and Friendly Relations

Article 1(2) of the UN Charter provides an aspirational framework for international relations by emphasizing the development of friendly relations among nations based on respect for equal rights and self-determination of peoples. This provision sets a broad, idealistic goal that guides state conduct without imposing a strict legal prohibition on every diplomatic affront, aiming instead to shape the ethos of international engagement (for an idealistic approach, see Grigory I. Tunkin, Co-existence and international law, The Hague academy of international law, Collected courses, vol. 95 (1958)).

While insults or offensive rhetoric between state leaders can strain diplomatic ties and undermine the spirit of amity envisioned by the Charter, such incidents do not legally violate Article 1(2). Rather, they highlight the challenge of aligning state behavior with the Charter’s goals of mutual respect and sovereign equality. The presence of hostile speech is a symptom of ongoing difficulties rather than a settled legal command forbidding every offense.

Having said that, breaches in diplomatic decorum are typically consequences of deeper issues rather than isolated provocations. Offensive speech is usually a symptom of already sour and inamicable relations, not their starting point. In other words, such rhetoric serves as an expression of deteriorated diplomatic ties rather than the cause.

Insults Provoking Moral Damage

International law recognizes claims for moral damage to reputation, dignity, or emotional suffering – when linked to an internationally wrongful act. The Permanent Court of International Justice in the Chorzów Factory case and Article 31(2) of the Articles on State Responsibility confirm that states are obliged to provide full reparation for any damage, be it material or moral.

However, successful claims for moral damage almost always involve serious violations such as unlawful detention, breaches of sovereignty, or significant reputational harm with tangible consequences. Remedies typically take the form of satisfaction – official apologies or declaratory judgments – rather than monetary compensation. This is mainly because moral damages are often subjective, and they’re very hard to quantify.

Claims based solely on insults are highly unlikely to succeed. Such claims typically arise only in exceptional circumstances involving grave violations like unlawful detention or substantial reputational damage with tangible consequences. This cautious approach aims to prevent the proliferation of speculative or minor claims and ensures that moral damages are reserved for genuinely serious breaches of international law. In other words, a State would need to demonstrate real and serious harm and establish jurisdiction before a competent international tribunal – a scenario that remains remote (see here, and here). This is, of course, assuming there is a competent forum to hear such claims in the first place.

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In sum, international law offers only narrow grounds for treating diplomatic insults as unlawful. The recent uptick in undiplomatic language among State officials often tracks the rise of populist and nationalist politics, where public insults serve both domestic and international agendas (see here and here). Domestically, such rhetoric helps leaders position themselves as outsiders challenging “elite norms” and appealing to popular sentiment. Internationally, it enables States to signal dissatisfaction or assert strength without foreclosing future cooperation.

The proliferation of social media and digital diplomacy has amplified the visibility and impact of these exchanges, making insults more immediate and widespread. Symbolic insults function as a form of calculated “diplomatic slap” – a tacit tool for balancing interests and restoring social status without severing engagement (for an international relations’ analysis, see here). As populist movements continue to shape global politics, it remains to be seen whether some heads of States will “have learnt to behave themselves” (to quote the government of the UK in the Corfu channel case), whether international law will adapt to address the changing tone of diplomacy, or whether, for now, sharp words will remain an accepted, if controversial, tool of statecraft.

Credit: Charles Maurice de Talleyrand-Périgord by François Gérard, 1808. Talleyrand is credited with saying of Napoleon: “What a shame that such a great man is so ill-mannered!” A fitting symbol for how diplomacy and offense often go hand in hand.