• Self-Defense is the anchor that orients the law of war.

• Military aggression is prohibited under international law, but the use of military force in self-defense is permissible under the United Nations Charter Article 51.

  • At some point, prohibited military aggression becomes justifiable self-defense.

  • The activity might look exactly the same, with battles on the ground and in the air, but the legal valence is just the opposite

• The problem for lawyers is fathoming the point of transformation when aggression becomes self-defense. The classification might be controversial.

• The challenge for us is to understand the relationship between the domestic and international laws of self-defense.

• The contours of self-defense in these two areas of conflict—individual conflict in domestic law and collective conflict in international law—are essentially the same.

• The positive, or written, law varies from place to place largely in the detail with which self-defense is described.

• The German statute, § 32, sums it up in a few words: “A defensive use of force is legitimate when necessary to avert an imminent unlawful attack to oneself or others.”

  • That is, in principle, an attack against any interest—life, limb, property, or freedom of movement—will suffice.

• The New York statute says: NYPL §35.15(1) A person may, subject to the provisions of sub-division two, use physical force upon another person when and to the extent he reasonably believes such to be necessary to defend himself or a third person from what he reasonably believes to be the use or imminent use of unlawful physical force by such other person, unless:

  • (a)  The latter’s conduct was provoked by the actor himself with intent to cause physical injury to another person

  • (b)  The actor was the initial aggressor

  • (c)  The physical force involved is the product of a combat by agreement not specifically authorized by law.

• The Rome Statute, establishing the International Criminal Court as of July 1, 2002, is our guide to international criminal law. The statute provides:

  • The person acts reasonably to defend himself or herself or another person or, in the case of war crimes, property which is essential for the survival of the person or another person or property which is essential for accomplishing a military mission, against an imminent and unlawful use of force in a manner proportionate to the degree of danger to the person or the other person or property protected

The Four DImensions of Self-Defense

• Imminence: The requirement of imminence means that the time for defense is now! The defender cannot wait any longer.

• Necessity: Force is never justified unless it is necessary.

  • The German Penal Code is explicit on this requirement.

  • The New York Penal Code requires that the actor “reasonably believes” the use of force “to be necessary to defend himself or a third person.”

  • The Rome Statute says nothing about necessity in defending persons, but as to property the statute is demanding

  • The requirement of necessity implies that the means chosen must be the least costly available

• Proportionality: Proportionality in self-defense requires a balancing of competing interests, the interests of the defender and those of the aggressor.

  • The rule of proportionality makes sense, but not all legal regimes require it.

• Intention: The consensus among Western legal systems is that in order to invoke a sound claim of self-defense, the defender must know about the attack and act with the intention of repelling it.

  • No harm, no crime. And there is arguably no harm in killing an aggressor.