The Conservative Case for International Law

The mayor’s legal team has concluded that New York City lacks the necessary authority to make the arrest, and instead, Mamdani urged the federal government to join the International Criminal Court (ICC) and execute its warrant against Netanyahu.

The Trump administration, unsurprisingly, has no intention of doing so. It has, rather, sought to paint the ICC—and, by extension, the operationalization of international law itself—as an existential threat to U.S. sovereignty. “As we speak,” Secretary of State Marco Rubio warned in a recent video message, “the ICC and its friends are waging a war against our country, not with bullets or missiles, but with statutes and compacts and the force of so-called international law.” Earlier this year, President Donald Trump was more blunt: “I don’t need international law,” he said following the U.S. seizure of Venezuelan leader Nicolás Maduro earlier this year.

But conservatives haven’t always been so hostile to international law. Indeed, some of the most prominent right-wingers of yore saw in it the sole foundation upon which a desirable world order could rest.

One such figure was Sen. Robert Taft, the Ohio politician who so thoroughly embodied mid-century conservatism that he earned the sobriquet “Mr. Republican.” Despite his unimpeachable GOP credentials, Taft was a passionate advocate of international law, as well as the robust mechanisms necessary to give it teeth. He viewed law as the only force strong enough and solid enough to prevent a third world war. As he argued in a 1949 speech opposing the North Atlantic Treaty:

[T]here is only one real hope of peace in the world to come—an association of nations binding itself to abide by a law governing nations and administered by a court of legal justice. Such a judicial finding must not be subject to veto by any nation and there must be an international force to enforce the court’s decree.

Similarly, Elihu Root—who helmed the War and State Departments under President Theodore Roosevelt, and later served as a Republican senator—believed fervently in the importance of international law and its enforcement. “Next to the preservation of national character,” he proclaimed in 1915, as World War I was killing off nearly an entire generation of European men, “the most valuable possession of all peaceable nations, great and small, is the protection of those laws which constrain other nations to conduct based upon principles of justice and humanity.”

Even that old arch-conservative Metternich, widely considered among the progenitors of foreign policy realism, believed states could legitimately act only so long as they remained within the compass of the law of nations. Not “blood and iron,” but “Kraft im Recht” was his heraldic motto—“strength in law.”

What happened?

International law is in some sense coeval with systems of states; traces can be detected as far back as the letters exchanged among the Bronze Age rulers of the Near East . But it was the 17th century jurist Hugo Grotius who gave us the first really coherent formulation. This was a vision of the jus gentium, basic rules binding all because of their derivation from natural law—that is, universal moral principles inherent in nature and discernible through reason. These rules require things like honoring treaties and respecting ambassadors, making war only for just causes and avoiding the deliberate harm of innocents, and allowing all nations freedom of the seas.

This understanding made slow but steady progress over the ensuing centuries. It was shaken by the French Revolution and the decades of war that ensued, reified again in the post-Napoleonic settlement, and regnant—at least among European nations—until August 1914, when the first total war of the industrial era sounded its death knell.

There were several reasons this older vision appealed to conservatives. It accommodated the belief that human affairs should be grounded in a transcendent moral order, and that conduct—whether at the individual or the collective level—must be measured against some sort of absolute standard. It purported to draw not just on natural law but customary usage, further enhancing its stature in the eyes of precedent-minded traditionalists.

It also reflected conservatives’ skepticism of man’s perfectibility (or even his capacity for significant improvement). In a fallen world, the natural selfishness and viciousness of our species poses a constant threat to collective welfare. Anarchy and civilizational breakdown are always possible; and just as maintaining a fragile order within nations requires the promulgation and enforcement of rules, so too does maintaining this order among them.

But after 1945, international law was developed and understood in a very different way. The old vision had apparently failed to prevent two cataclysmic world wars; perhaps something more revolutionary and intrusive was needed. A complex web of international organizations began to emerge, which aimed to coordinate the world’s growing interdependence both by expanding into previously unregulated domains (e.g., monetary policy and public health) and, most significantly, by reaching inside states, often in the name of human rights.

Perhaps the most notorious example of this was the “responsibility to protect.” This concept, which emerged from diplomat Francis Deng’s earlier notion of “sovereignty as responsibility” (which made sovereignty conditional rather than absolute), allowed the claims of non-state actors to be wielded to chip away at states’ sovereignty. It and similar developments threatened what had heretofore been a foundational or constitutional principle of international law: namely, that governments were its sole legitimate subjects.

Thus, this vision sought to transform international law from something that was constitutive of world order into a force that—by introducing a destabilizing, purposive function—actively threatened it. As the great IR theorist Hedley Bull noted five decades ago:

Carried to its logical extreme, the doctrine of human rights and duties under international law is subversive of the whole principle that mankind should be organized as a society of sovereign states. For, if the rights of each man can be asserted on the world stage over and against the claims of his state, and his duties proclaimed irrespective of his position as a servant or as a citizen of that state, then the position of the state as a body sovereign over its citizens, and entitled to command their obedience, has been subject to challenge… The way is left open for the subversion of the society of sovereign states on behalf of the alternative organizing principle of a cosmopolitan community.

There are, then, two types of international law. The first is law among states: horizontal and in some sense procedural, designed to support pluralism, facilitate trade, and contain the risks of conflict. The second is law over states: vertical, purposive, and homogenizing, susceptible to hijacking by elites who would revolutionize the present political organization of the world in the service of utopian dreams.

Conservatives have good reason to oppose the second interpretation. But the first, which has historically commanded considerable allegiance on the right, deserves another hearing.

Because without it, we are left with nothing but the law of the jungle.

Witness the so-called flexible realism promulgated by the Trump administration. It has, in practice, proved to be a cover for simple predation: the strong taking what they will, and the weak suffering what they must. The United States has used its immense power to threaten the seizure of Greenland from a treaty ally on a baseless pretext, spirit away the leader of Venezuela and claim as much of its oil as possible, and starve the Cuban people into submission to effect regime change. (And that’s just in the Western hemisphere.)

What we would condemn in an individual, much of the right has been willing to tolerate—even celebrate—in a nation. But obviously this view is untenable: Our ethical obligations are not somehow waived when we come together to act as a commonwealth. Nor do the basic rules that apply to societies of individuals cease altogether to govern societies of states.

At this point, some conservatives may object on realist grounds. Hasn’t recent history—particularly the excesses of the war on terror—shown conclusively that moralism should be kept as far away from foreign policy as possible?

We would reply that one can have morality without moralism. The critical distinction is the treatment of domestic affairs; we hold with Taft that international law must account for the fact that

Interference in domestic policies… [is] more likely to make war than to prevent it. The test is: is the subject one on which the people of the United States would be willing to have other nations interfere with our internal actions? If not, we should not attempt to impose such interference on others.

Once stripped of the emphasis on human rights and the imperative to remake societies, international law is in practice cautious and prudential. Indeed, it is no coincidence that the two most egregious disasters of recent U.S. foreign policy—the Iraq and Iran wars—could not have been launched by administrations that took international law seriously.

Conservatives have also historically distinguished between liberty—the authentic use of freedom, which depends upon self-discipline and the observation of a higher law—and license—the abuse of freedom, the indulgence of every base appetite and selfish impulse without compunction or constraint. What must be avoided is the invocation of realism as an excuse or justification for license on a global scale. Rather, the proper use of realism is as a guide, a way to steer the ship of state through the world as it is, toward those far shores of peace, prosperity, and virtue.

Israeli Prime Minister Benjamin Netanyahu and U.S. President Donald Trump in Tel Aviv, Israel, on Oct. 13, 2025. Chip Somodevilla/Getty Images

As for Netanyahu, at least one of the charges on which both the ICC and Mamdani want him booked is squarely within the domain of international law. This is the accusation of war crimes, specifically the use of “starvation as a method of warfare” and “intentionally directing an attack against the civilian population.” These would be crimes whether or not the ICC existed, and the United States is obliged to treat them as such, even though it has not acceded to the Rome Statute that established the court. (Israel’s actions implicate the Geneva Convention and the strictures of the UN Charter, both of which Washington is party to, as well as the traditional understanding of the laws of war.)

Obviously, there is no prospect of a change of heart on this issue from the White House. But 2028 is on the horizon; and as we inch ever closer to a post-Trump future, those conservatives interested in buttressing world order, protecting U.S. interests, and promoting the common good should return to the wisdom of their forebears—and take another look at international law.