This is the text of a speech to the Institute for Policy Research in London on October 24, 2006.

People who write about war — and many do — generally end up writing about the wars of their own place and time. From the start, legal questions have been at the center of debates about my own country’s recent wars, none more than our current "global war on terror." Is Guantanamo an egregious violation of the law in war or a legitimate use of the President’s Constitutional power as Commander in Chief? Was the Coalition invasion of Iraq authorized by prior UN Security Council resolutions? Was it a legitimate act of preventive self-defense — or yet another example of the American administration’s disinterest in the multilateral legal framework it had taken more than a generation to build?

Today, political leaders and their lawyers scurry to answer these questions with a blur of arguments about what the law permits. Opponents of administration policy find it easier to raise legal than political questions. And the administration finds it easier to defend the President’s legal prerogatives than his policies.

This afternoon, I’d like to step back from these immediate controversies, to explore three ideas.

First, modern war as a legal institution. Once a bit player in military conflict, law now shapes the institutional, logistical and physical landscape of war.

Second, modern law is surprisingly fluid. International law is no longer an affair of clear rules and sharp distinctions. Indeed, as law became an ever more important yardstick for legitimacy, legal categories became far too spongy to permit clear resolution of the most important questions — or became spongy enough to undergird the experience of self-confident outrage by parties on all sides of a conflict.

And finally, I’d like to explore the opportunities and dangers opened up by war as a modern legal institution. When things go well, law can provide a framework for talking across cultures about the justice and efficacy of wartime violence. More often, I am afraid, the modern partnership of war and law leaves all parties feeling their cause is just and no one feeling responsible for the deaths and suffering of war. Good legal arguments can make people lose their moral compass and sense of responsibility for the violence of war.

So, first, modern war as a legal institution.

What could it mean to say that war has become a legal institution — or that war is the continuation of law by other means? Not that everyone always follows the rules — or that everyone agrees on what the rules are or how they should be interpreted.

War is a legal institution first because it has become a professional practice. Today’s military is linked to the nation’s commercial life, integrated with civilian and peacetime governmental institutions, and covered by the same national and international media. Officers discipline their force and organize their operations with rules.

Some years ago, before the current war in Iraq, I spent some days on board the USS Independence in the Persian Gulf — nothing was as striking about the military culture I encountered there as its intensely regulated feel. Five thousand sailors, thousands of miles from base, managing complex technologies and weaponry, constant turnover and flux. It was absolutely clear that even if I could afford to buy an aircraft carrier, I couldn’t operate it — the carrier, like the military, is a social system, requiring a complex and entrenched culture of standard practices and shared experiences — rules and discipline.

Mobilizing "the military" means setting thousands of units forth in a coordinated way. Delicate political arrangements and sensibilities must be translated into practical limits — and authorizations — for using force.