Separation of Powers

How to Preserve Liberty in Troubled Times

Author Cass R. Sunstein On Tour
$24.95 US
The MIT Press
12 per carton
On sale Feb 17, 2026 | 9780262051774
Sales rights: World

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Why the separation of powers is essential to liberty and democracy.

From the winner of the Holberg Prize and New York Times–bestselling author of The World According to Star Wars.


All over the world, people are questioning the separation of powers. They want a strong man, able to do what must be done. But James Madison was right to say this: “The accumulation of all powers, legislative, executive, and judiciary, in the same hands, whether of one, a few, or many, and whether hereditary, self-appointed, or elective, may justly be pronounced the very definition of tyranny.”

In this essential and immensely timely book, Separation of Powers, Cass Sunstein explains why the separation of powers is necessary for both freedom and self-government. He shows that freedom from fear is a central goal of the system of separation of powers. He also explains why the executive branch is the most dangerous branch, why the idea of presidential immunity is a terrible one, and why an independent judiciary is crucial.

Drawing on his extensive experience in the White House, the Department of Justice, and the Department of Homeland Security, the author also argues that the separation of powers is, in fact, six separations of powers: (1) The legislature may not exercise the executive power. (2) The legislature may not exercise the judicial power. (3) The executive may not exercise the legislative power. (4) The executive may not exercise the judicial power. (5) The judiciary may not exercise the legislative power. (6) The judiciary may not exercise the executive power. Each of these is essential to liberty under law.
ENDORSEMENTS

“James Madison once noted that questions about the separation of powers ‘puzzle the greatest adepts in political science.’ Cass Sunstein ranks high among today’s greatest adepts, and his deft analysis in this brief but incisive book demonstrates why.”
—Jack Rakove, William R. Coe Professor of History and American Studies and Professor of Political Science, emeritus, Stanford University; author of Original Meanings

Separation of Powers is as powerful as it is timely. Subtly drawing parallels between Nazi Germany’s obedience to its führer and the current obsequious treatment of the leader of the United States, Sunstein mounts a devastating attack on the Supreme Court’s recent decisions that undermine the separation of powers and threaten the liberty that the separation of powers has protected for nearly 250 years.”
—Jack Beermann, Philip S. Beck Professor of Law, Boston University

“Cass Sunstein never disappoints. This book will make everyone stop and think about the separation of powers. Progressives will like his critique of the ‘Grand Narrative’ of separation of powers that is now dominating the Supreme Court. Conservatives and libertarians will be intrigued by his description of how ‘partyism’ is weakening the separation of powers that is essential to protecting our liberty. A good read.”
—Randy Barnett, Patrick Hotung Professor of Constitutional Law, Georgetown University Law Center; Faculty Director, Georgetown Center for the Constitution; author of A Life for Liberty

“As the separation between our branches becomes increasingly blurred, and the executive sweeps more powers into its gaping maw, Cass Sunstein’s terrific, trenchant, and timely tome becomes required reading. Read it now and relearn why we should all bet on the separation of powers.”
—Saikrishna Prakash, James Monroe Distinguished Professor of Law, University of Virginia

“Cass Sunstein writes from long experience; he has thought about these questions for decades. Clear, earnest, and incisive, this book is an advanced introduction to some of the most important ideas in American constitutionalism.”
—Jack Balkin, Knight Professor of Constitutional Law and the First Amendment, Yale Law School

“Both timely and timeless, Separation of Powers offers a trenchant analysis of a key structural feature of the U.S. government aimed at protecting against tyranny. Anyone concerned about the growth of unchecked executive power in the United States will benefit from reading this book.”
—Cary Coglianese, Edward B. Shils Professor of Law and Professor of Political Science, University of Pennsylvania; Director, Penn Program on Regulation

About

Why the separation of powers is essential to liberty and democracy.

From the winner of the Holberg Prize and New York Times–bestselling author of The World According to Star Wars.


All over the world, people are questioning the separation of powers. They want a strong man, able to do what must be done. But James Madison was right to say this: “The accumulation of all powers, legislative, executive, and judiciary, in the same hands, whether of one, a few, or many, and whether hereditary, self-appointed, or elective, may justly be pronounced the very definition of tyranny.”

In this essential and immensely timely book, Separation of Powers, Cass Sunstein explains why the separation of powers is necessary for both freedom and self-government. He shows that freedom from fear is a central goal of the system of separation of powers. He also explains why the executive branch is the most dangerous branch, why the idea of presidential immunity is a terrible one, and why an independent judiciary is crucial.

Drawing on his extensive experience in the White House, the Department of Justice, and the Department of Homeland Security, the author also argues that the separation of powers is, in fact, six separations of powers: (1) The legislature may not exercise the executive power. (2) The legislature may not exercise the judicial power. (3) The executive may not exercise the legislative power. (4) The executive may not exercise the judicial power. (5) The judiciary may not exercise the legislative power. (6) The judiciary may not exercise the executive power. Each of these is essential to liberty under law.

Praise

ENDORSEMENTS

“James Madison once noted that questions about the separation of powers ‘puzzle the greatest adepts in political science.’ Cass Sunstein ranks high among today’s greatest adepts, and his deft analysis in this brief but incisive book demonstrates why.”
—Jack Rakove, William R. Coe Professor of History and American Studies and Professor of Political Science, emeritus, Stanford University; author of Original Meanings

Separation of Powers is as powerful as it is timely. Subtly drawing parallels between Nazi Germany’s obedience to its führer and the current obsequious treatment of the leader of the United States, Sunstein mounts a devastating attack on the Supreme Court’s recent decisions that undermine the separation of powers and threaten the liberty that the separation of powers has protected for nearly 250 years.”
—Jack Beermann, Philip S. Beck Professor of Law, Boston University

“Cass Sunstein never disappoints. This book will make everyone stop and think about the separation of powers. Progressives will like his critique of the ‘Grand Narrative’ of separation of powers that is now dominating the Supreme Court. Conservatives and libertarians will be intrigued by his description of how ‘partyism’ is weakening the separation of powers that is essential to protecting our liberty. A good read.”
—Randy Barnett, Patrick Hotung Professor of Constitutional Law, Georgetown University Law Center; Faculty Director, Georgetown Center for the Constitution; author of A Life for Liberty

“As the separation between our branches becomes increasingly blurred, and the executive sweeps more powers into its gaping maw, Cass Sunstein’s terrific, trenchant, and timely tome becomes required reading. Read it now and relearn why we should all bet on the separation of powers.”
—Saikrishna Prakash, James Monroe Distinguished Professor of Law, University of Virginia

“Cass Sunstein writes from long experience; he has thought about these questions for decades. Clear, earnest, and incisive, this book is an advanced introduction to some of the most important ideas in American constitutionalism.”
—Jack Balkin, Knight Professor of Constitutional Law and the First Amendment, Yale Law School

“Both timely and timeless, Separation of Powers offers a trenchant analysis of a key structural feature of the U.S. government aimed at protecting against tyranny. Anyone concerned about the growth of unchecked executive power in the United States will benefit from reading this book.”
—Cary Coglianese, Edward B. Shils Professor of Law and Professor of Political Science, University of Pennsylvania; Director, Penn Program on Regulation