I don’t know the details of how it happened, but I am pretty sure the assassination of Osama bin Laden required presidential authorization from Barack Obama (I don’t know why, though - if it were an act of war, couldn’t a lower-ranking officer such as a general have carried it out?)

I do not know what the range of views are on the legality of this action, but I assume the status quo is that it was valid as an “act of war”.

This makes me want to know to what extent there is an unambiguous way of determining the scope of an “act of war”. In principle, could the U.S. president do anything, and claim it was an “act of war”? Is this more a political matter than a legal one: nobody is going to take the president to trial, unless there happens to be huge opposition from another political group, or something?


  1. What does the law explicitly say is an “act of war”; ie when can the President invoke it and what does it encompass?
  2. If the wording is ambiguous, are there any consistent precedents by which modern day lawyers may argue which actions are or are not valid acts of war?
  3. Whether or not an act of war is well-defined or not, is it simply never going to be brought to court unless there is political opposition?

Because that last point might bother me - that our legal system isn’t designed to be automatically applied, but only if someone has an interest in doing so. It seems like this could be the basis for flouting so many laws: it was declared illegal, but nobody cares about you, so the law isn’t going to protect you, because your life isn’t worthy of anybody’s time; or something.

  • 3
    What law are you talking about? What makes you think that "acts of war" is a legally relevant phrase? You seem to be making a lot of assumptions without saying what they are.
    – ohwilleke
    Commented Jan 25 at 3:04

2 Answers 2


An act of war is one taken during war or intended to provoke one.

While the "Global War on Terror" was practically a war, it was not a declared war. Calling in colloquially a war doesn't make everything done during it an "act of war."

The attack on OBL was undertaken on a sovereign nation's territory, but certainly wasn't intended to provoke war with Pakistan. I would classify it more as harsh diplomacy, and because it was taken against a person generally considered an enemy of the state, easily justified at least in the USA. But clearly an attack on another sovereign nation's soil will require Presidential approval.

Acts of war aren't documented in writing, but by consensus. There was a league of Nations treaty, but this was mostly just writing down what everyone already thought. Typical acts would include:

  • Attacks on citizens or armed forces
  • Invasion
  • Blockade of commerce
  • Material support of internal combatants

These things aren't cut and dried; war is a political thing and is clearly affected by the political climates of the involved parties.

  • So Pakistan could have construed the action as an act of war, but it didn't do that -- for various political reasons.
    – o.m.
    Commented Jan 25 at 15:09

One place where the term Act of War is defined is 18 U.S. Code § 2331 - Definitions

act of war

(4) the term “act of war” means any act occurring in the course of— (A) declared war; (B) armed conflict, whether or not war has been declared, between two or more nations; or (C) armed conflict between military forces of any origin;

This definition is for the limited purpose of interpreting Chapter 113B of 18 U.S.C., which sets out criminal offences and civil remedies relating to terrorism.

For the purpose of Chapter 113B, an act of war requires an open, declared war. The last declared war by the USA was 1945 against Romania, Bulgaria and Hungary.

In the alternative, it requires an armed conflict between nations. Such was the case in Korea, Kuwait/Iraq and Ex-Yugoslavia.

In the alternative, it requires [organized] military forces. Military forces in this sense, as opposed to terrorist organizations, seem to be organized forces, such as a proper Militia or other combatant units under the Geneva Conventions.

2332f and 2332i distinguish military forces from non-military forces such as Al Qaeda, offering the military the protection of the laws of war, which again, would be the Hague and Geneva conventions.

The first time and only time that definition is used in the chapter is in 18 USC §2336, where Terrorism and Acts of War are defined as never overlapping. Any action that is a proper act of war is never terrorism:

(a)Acts of War.— No action shall be maintained under section 2333 of this title for injury or loss by reason of an act of war.

The term may have other meanings in other contexts.

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