Criticism, on the contrary, deciding all questions according to the fundamental laws of its own institution, secures to us the peace of law and order, and enables us to discuss all differences in the more tranquil manner of a legal process. In The Science of Right Kant discusses the right of nations and international law and also the universal right of mankind. Ethically, people ought to be treated as ends in themselves and not mechanically as a means to some end. Therefore the ruler has no right to treat his people as objects for some warlike purpose. As such they must give their free consent, through their representatives, not only to the carrying on of war generally, but to every separate declaration of war.
Neutrality is the right to remain at peace when a war is nearby.
Alliance is the right of federation, that states may defend themselves in common against attack. However, there is no right of alliance for external aggression or internal aggrandizement. Kant points out that nations, like individuals, must enter into a legal state, in this case, a union of states, which is the only way to establish peace and the public right of nations. Thus a permanent congress of nations must eventually become practical so that differences may be settled by means of a civil process instead of by barbarous war. Kant bases the right to a universal peaceful union of all nations on the juridical principle of legal justice rather than on the moral ideal of the philanthropic or ethical principles.