The return of Donald Trump to the U.S. presidency has brought a resurgence of the “America First” approach, raising new challenges to international law and norms. While during its first term, the Trump administration reiterated its support for “a bedrock international principle” when it called on Russia to end its illegal occupation of Crimea, early actions and proposals of the new Trump administration signal a willingness to sidestep or outright defy longstanding principles of sovereignty and human rights.
Striking examples include President Trump’s proposal concerning Gaza, which involves evacuating the Gazan population and remaking the territory, statements suggesting acceptance of Russia’s hold on occupied Ukrainian territories rather than demanding a full withdrawal, and his refusal to rule out the use of force to take control of the Panama Canal or Greenland. These developments, accompanied by withdrawal from and rejection of international institutions and agreements, illustrate a broader pattern of U.S. policy under Trump that erodes the bedrock principles of the international community and tests the limits of international law. We may be effectively reverting, at least temporarily, to an era of imperial rule.
Recent Trends
It is important to note that the Trump administration is not solely responsible for ushering in this precarious era. Its actions may simply reflect a reaction to challenges to the global order posed by Russia and China. Nevertheless, there is a significant difference between invoking international law in the service of partisan agendas and outright disavowing it. Upon attacking Kyiv, Russian President Vladimir Putin crafted a justification rooted in international law, albeit misapplied to support an illegal invasion. A flawed articulation of the law serves to reinforce the law rather than to deny its existence (1986 Nicaragua judgment). Ignoring international law altogether is perhaps less disingenuous than manipulating it, but it is arguably even more sinister because it rebuffs even the expectation to be accountable to others, rejecting the bedrock principle of sovereign equality.
This rejection goes to the heart of contemporary international law. Ingrid Brunk and Monica Hakimi (2024) identify the post 1945 international legal order as safeguarded by a triad of overlapping norms: the sanctity of borders, the prohibition on the use of force, and respect for national self-determination. They emphasize that “the project of territorial entrenchment” is critical to ensuring that “state authority in any given territory [is] not susceptible to disruption or revision.” They therefore rightly conclude that the prohibition on forcible annexation has the status of jus cogens.
The project of territorial entrenchment was long in the making but crystallized with the adoption of the UN Charter in 1945, reaching full fruition during the decolonization processes of the 1960s and 1970s. For these norms to function effectively, a global enforcement mechanism was required. This mechanism took shape in the early 1990s when the U.S.-dominated UN Security Council asserted its authority. As is typical of effective systems that protect property rights, this arrangement fostered economic globalization, improved global welfare, enhanced trust in international institutions, and bolstered commitment to shared goals and values in an interdependent global economy. These favorable trends were mirrored in the significant decline in global military spending between 1990 and 1998 (here).
However, this brief era of relative trust in the rule-based global system began to erode as serious conflicts of interest emerged between the most powerful nations that had been serving as its enforcers, highlighted by the Kosovo and Iraq wars, China’s forceful actions to enforce its territorial claims in the South China Sea, and Russia’s occupation of parts of Georgia and later Crimea. Since 2011, cooperation between China and Russia to block the Security Council (here and here) has marked the end of P5 unity in securing international peace and security. Since 1998, global military expenditure has been steadily increasing, with 2014 marking the beginning of a significant upward trend (here).
If trends in military spending reflect social expectations—and if those expectations are self-fulfilling—a new era of colonial domination may be on the horizon, shaped by three nuclear powers that dominate the UN Security Council and view international law – if they recognize it at all – as pliable to their needs.
The Law Could Not Be Clearer
Arguably, in its Advisory Opinion of July 2024 on Legal Consequences Arising from the Policies and Practices of Israel in the Occupied Palestinian Territory, Including East Jerusalem, the International Court of Justice (ICJ) took account of several outstanding threats to concept of territorial entrenchment. Its opinion reflects the culmination of a collective human effort to construct, refine, and protect a rule-based international legal order founded on the principle of sovereign equality, supported by international institutions and courts.
The court was unequivocal: territorial sovereignty is not subject to external legal challenge. The exercise of permanent control over foreign territory without the permission of the sovereign, regardless of the circumstances in which such control was established, constitutes annexation and is therefore unlawful. The court defined annexation as “the forcible acquisition by the occupying Power of the territory that it occupies, namely its integration into the territory of the occupying Power.”
The ICJ also emphasized that occupation does not need to be “belligerent” to fall under this definition, referring broadly to the “law of occupation” rather than the narrower “law of belligerent occupation.” This broader terminology underscores the principle that foreign control must be strictly limited and regulated, even when it does not arise from physical military presence. Permanent control is prohibited and can only be justified under international law through military necessity, as any “use of force [that is] subject to the rules of international law governing the legality of the use of force or jus ad bellum.”
Can the Law Survive in the Age of Empire?
What impact can this comprehensive articulation of international law have in practice, when nuclear powers with veto authority in the Security Council invoke (or ignore) the law to justify aggression and denial of self-determination?
Three overlapping responses to challenge any state’s rejection of the project of territorial entrenchment are theoretically possible:
Collective Action by States:
International law obliges states to act collectively in response to violations. The ICJ has affirmed that prohibitions on annexation and violations of self-determination are erga omnes obligations, requiring all states to refrain from recognizing or supporting such unlawful actions. States must also prevent economic or trade relations that perpetuate such illegal situations. As Olivier Corten and Vaios Koutroulis have shown, the international response to Russia’s actions has been overwhelming, with most states unequivocally denouncing the attack (while the rest, except Syria, stopped short of accepting Russia’s claim of self-defense). But under the new approach of the Trump administration, such a resolute response might be short-lived.
Institutional Responses:
States can also react through international organizations (IOs), primarily the UN Security Council. It is noteworthy that in its 2024 Opinion, the ICJ saw the duty of non-recognition as applicable also to IOs, “including the United Nations.” Departing from its cryptic message about the law applicable to IOs (in the 1980 Opinion on Interpretation of the Agreement of 25 March 1951 between the WHO and Egypt), the ICJ asserted that IOs are obliged not to recognize as legal “serious breaches of obligations erga omnes under international law.” But with three P5 members turning their backs on the law, the UN is unlikely to react to such breaches.
The Transnational Legal Process:
The third response is through what Harold Koh referred to as “resistance” through a “transnational legal process” involving judges of domestic and international courts, bureaucrats in domestic and international agencies, civil society, and private entities. But resistance through the transnational legal process requires the active participation of various actors within democracies that remain resilient against populism and are strong enough to withstand pressure from the three superpowers.
When the law is ignored by some and not effectively resisted by others, this is the age of empire. However, if we take – as we must – the principle of jus cogens seriously, we must note that international law is not dead even during the reign of empire. It hibernates until the opportune moment arises.
Hence, a fourth response might become necessary:
It would be the role of lawyers and historians to document and preserve the law as it stands, awaiting a time when the global order can be restored. History has demonstrated that international law has a long memory. The Baltic republics, for instance, survived an unlawful annexation and regained their sovereignty after fifty years of Soviet occupation. When the USSR collapsed, the world promptly recognized their restored independence. The same can, and must, happen if Ukraine is forced to acquiesce to a Russian-American dictate or if Palestinians are forced to leave Gaza.
The project on territorial entrenchment, like other jus cogens norms such as the prohibition on aggression and the right to self-determination, will remain valid even during the age of empire, even as emperors outright deny the relevance of international law. Unless a new customary norm emerges, the law remains intact. As the ILC has stated concerning the modification of jus cogens norms through new practices: “Acceptance and recognition by a very large and representative majority of States is required for the identification and modification] of a norm as a peremptory norm of general international law (jus cogens).”
Therefore, unilateral acts or agreements that deviate from jus cogens norms—such as those norms protecting the right to self-determination or prohibiting the use of force and annexations—will not affect the validity of sovereign borders. While the world faces an increasingly uncertain future, it is somewhat reassuring that a few fundamental norms of international law will continue to hold until a more stable global order is achieved. What remains imperative is law-abiding states (which constitute the vast majority), lawyers, scholars, historians, and civil society continue to reinforce the long-term validity of those fundamental norms in the face of attack even by powerful actors and their allies.