ABSTRACT
As the natural law of nations gave way to positive international law, the just war tradition gave way to a more legalistic standard. The UN Charter prohibits any threat or use of force except in self-defense or by Security Council authorization. The Definition of Aggression (1974) attempts to clarify what it means to use force. The amended Rome Statute holds states’ leaders personally accountable for the crime of aggression. However, a plethora of new problems and unresolved old ones pose challenges to complying with the very restrictive jus ad bellum of today. Several extra-Charter justifications for force have been advanced in recent years, including protection of nationals, anticipatory self-defense, humanitarian intervention, anti-terrorism, and anti-criminal operations.
