Jus ad bellum (Latin for "right to wage war") is a set of criteria that are to be consulted before engaging in war, in order to determine whether entering into war is permissable; that is, whether it is a just war.
Jus ad bellum is sometimes considered a part of the laws of war, although the term "laws of war" can also be considered to refer to jus in bello, which concerns whether a war is conducted justly (regardless of whether the initiation of hostilities was just).
An international agreement limiting the justifiable reasons for a country to declare war against another is concerned with jus ad bellum. In addition to bilateral non-aggression pacts, the twentieth century saw multilateral treaties defining entirely new restrictions against going to war. The three most notable examples are the Kellogg-Briand Pact outlawing war as an instrument of national policy, the London Charter (known also as the Nuremberg Charter) defining "crimes against peace" as one of three major categories of international crime to be prosecuted after World War II, and the United Nations Charter, which binds nations to seek resolution of disputes by peaceful means and requires authorization by the United Nations before a nation may initiate any use of force against another, beyond the inherent right of self-defense against an armed attack. By contrast, agreements defining limits on acceptable conduct while already engaged in war are considered "rules of war" and are referred to as the jus in bello. Thus the Geneva Conventions are a set of "jus in bello". Doctrines concerning the protection of civilians in wartime, or the need for "proportionality" when force is used, are addressed to issues of conduct within a war, but the same doctrines can also shed light on the question of when it is lawful (or unlawful) to go to war in the first place.
These terms are used in discussions of international law and philosophy.
People have tried to reconcile the competing moral principles of nonviolence/violence, and the evil of taking a human life with the need to protect an innocent human life, or your own, or no lives needed to be protected at all, through the use of force. The essential six elements for "The Just War Framework" that is the way to reason a violent act, are as follows:
* Just cause;
* Proper authority;
* Right intention;
* Reasonable prospect of success;
* Last resort