Do Checks and Balances Still Apply in Foreign Affairs?

Harold Hongju Koh being sworn in by former Secretary fo State Hillary Rodham Clinton in 2009
Professor Harold Hongju Koh at his 2009 swearing-in ceremony as Legal Adviser to the U.S. Department of State. Koh was sworn in by former Secretary of State Hillary Clinton ’73.

In his new book The National Security Constitution in the 21st Century (Yale University Press, 2024), Professor Harold Hongju Koh returns to the questions that he has wrestled with throughout his career. The new title, a wide-ranging expansion of Koh’s award-winning 1990 book, argues that the United States has veered from the constitutional checks and balances that must guide national security policy. To bring his argument into the present, Koh draws upon nearly five decades of experience both studying and shaping national security law as a law professor and as a government official in presidential administrations of both parties.

cover of the National Security Constitution in the 21st Century by Harold Hongju Koh

The “National Security Constitution” is itself a concept that Koh first developed in a much-cited 1988 Yale Law Journal article. The term describes a set of constitutional and subconstitutional norms that establish foreign affairs as a power shared between the presidency, Congress, and the judiciary. “In foreign as well as domestic affairs,” Koh writes, “the Constitution requires that we be governed by separated institutions sharing foreign-policy powers.”

While the National Security Constitution forbids unilateral control by any single government branch, Koh traces how presidents have claimed foreign affairs as their own to decide. He argues that all too often, the other two branches of government have complied, acquiescing in a concerted and expanding pattern of executive unilateralism.

“When national-security threats arise,” Koh writes, “weak and strong presidents alike have institutional incentives to monopolize the response; Congress has incentives to acquiesce; and courts have incentives to defer.” The National Security Constitution, Koh finds, has given way to “an interactive dysfunction,” which threatens the balance of power vital to U.S. constitutional democracy.

Koh’s new volume deepens and updates arguments he first raised when The National Security Constitution: Sharing Power after the Iran-Contra Affair was published in 1990. As its subtitle suggests, Koh grappled with the then-unfolding Iran-Contra affair, finding that the scandal was not an “aberration,” but rather, reflected a longer history of the White House encroaching on foreign affairs. The new volume takes Koh’s thesis both backward to the beginning of the republic as well as forward to the Biden administration’s actions in Ukraine and Gaza. Over time, Koh argues, we have come from seeing the president as our main protector from national security threats to seeing the president as a national security threat, as illustrated, for example, by the Trump administration’s once and perhaps future contempt for constitutional norms. This threat would not evaporate if Trump is defeated in the polls, because, Koh argues, Democratic presidents have undercorrected for the abuses of their unilateralist predecessors, and have engaged in “reactive unilateralism” when they cannot get congressional support for their initiatives, for example, the Biden administration’s recent immigration policies.

In short, Koh argues, the constitutional problem is lingering and structural, and will not be corrected just by voting out any particular administration. It would take only one more national election for the problem of extreme unilateralism to recur. The National Security Constitution, Koh argues, urgently needs to be restored for the 21st century. He reimagines the interlocking incentives that have long discouraged the White House, Congress, and the courts from curbing presidential power. 

“To prevent recurrence,” Koh concludes, “we must look for structural solutions aimed at promoting regularized interbranch communication, encouraging executive accountability, and revitalizing Congress and the courts as institutional counterweights to the president.” Calling our only alternatives “acceptance, despair, or reform,” his concluding chapters offer an array of creative structural solutions. 

Harvard Law School’s Laurence Tribe calls Koh’s book “quite simply the best ever written about its daunting subject […, w]ritten with the perspective that only experience can nurture, the wisdom that no amount of experience can ensure, and the brilliance that alone can bring wisdom and experience into alignment.” Former Secretary of State John Kerry calls Koh “an extraordinary public intellectual capable of dexterously operating at the highest levels of academia, government, and multilateral fora with equal skill and insight.”

Koh, Sterling Professor of International Law at Yale Law School, is one of the country’s leading experts in public and private international law, national security law, and human rights. He began teaching at Yale Law School in 1985 and served as its 15th Dean from 2004 until 2009. He has held a wide range of positions in public service: Senior Adviser in the Biden State Department’s Office of the Legal Adviser, State Department Legal Adviser in the Obama administration, Assistant Secretary of State for Democracy, Human Rights, and Labor in the Clinton administration, and Attorney-Adviser in the Reagan Justice Department’s Office of Legal Counsel. Koh has received 18 honorary degrees — most recently in 2024 from the University of Toronto — more than 30 awards for his human rights work, and lifetime achievement awards from Columbia and Duke Law Schools, the 2024 Burton Awards, and the ABA International Law Section. He has authored or co-authored nine books, published more than 250 articles, testified regularly before Congress, and litigated numerous cases involving international law issues in both U.S. and international tribunals, including ongoing representation of Ukraine against Russia before the International Court of Justice.