But while usage is the older and original source of international law, treaties are a later source of increasing importance. Un til recently these treaties generally had their international effect only when the rule con tained in them came to be gradually adopted by other nations and thus became part of the customary law, as, for example, the Dec laration of Paris of 1856 ; but with the es tablishment of The Hague Conferences there have come into existence conventions of a law-making character, in that they are sign ed and ratified by the nations as a body.
State Sovereignty and Its Corollaries. The subjects of international law are sov ereign states. The fundamental principles recognized by international law are that these states are independent each of the oth ers in all that regards their domestic affairs, that they possess certain territory over which they have complete jurisdiction, and that they are all legally equal. Under these three principles it will be found convenient to group the chief rules of international law.
As a consequence of the sovereignty and independence of the states which form the family of nations, each state has a right to enter into such treaties and alliances with other states as it may find necessary or con venient. In order to maintain their inde pendence the states of Europe have found it necessary from time to time to enter into alliances by which they have sought to •main tain a balance of power. These alliances are an expression of the danger to the inde pendence of states which might arise if any one of them should acquire a position of dominance. This necessity of maintaining a balance of power has led to the practice of intervention (q. v.) by which states have at times interfered in the affairs of other states. Intervention is ultimately based up on the principle of self-preservation, as the first law of international relations as of na ture.
The principle of the equality of states is illustrated in the whole history of interna tional relations from the time of the Treaty of Westphalia in 1648. Switzerland and Belgium, for example, have been recognized as having equal rights with Great Britain and Russia. But, while this legal equality is recognized, there is no denial of the fact that certain of the Great Powers have ex ercised a predominating influence in inter national relations.
Over the territory within their boundaries as well as over the persons residing in that territory, states have complete jurisdiction. State territory may be acquired in several ways: by discovery followed by occupation ; by military conquest followed by subjuga tion; by prescription ; and by accretion. It is recognized that a maritime belt, tradition ally measured by a marine league from the shore, is part of the territory of the state which it surrounds. See TERRITORIAL WA TERS. When the boundary between two states is marked by a river, the river takes on an international character, and apart from special cases determined by treaty, the mid-channel of the river constitutes the dividing line between the two countries. A
river is likewise recognized as being inter national in character when it flows through two or more countries, though this is for purposes of commerce and does not exclude the jurisdiction of each state over that por tion of the river within its domains. See RIVERS. Moreover, when a narrow body of water forms a passage way between two por tions of the open sea or between the open sea and a bay or gulf open to the commerce of the world, the canal or strait assumes an international character and is open to the commerce of the world, subject to the purely administrative restrictions or tolls imposed by the power controlling the canal Or strait.
After many struggles between maritime powers with conflicting interests, the open sea has come to be regarded as insuscepti ble of appropriation by any single state and as possessing, therefore, a purely interna tional character. No state can exercise ju risdiction over the vessels of another state sailing the high seas, nor assume any ex clusive right of fishing in certain waters not within the three-mile belt. See SEA.
The jurisdiction of a state over the per sons residing within its domains gives rise to rules of international law when such per sons happen to be citizens of another state. For many years it was held that a man could not, of his own accord, throw off his allegiance to one country and adopt the citizenship of another. While the United States courts recognized this principle, the Executive Department made constant efforts to obtain from European powers an acknowl edgment of the right of Expatriation (q. v.), and in 1868 Congress passed an act in which the right was declared to be a "natural and inherent" one, but many foreign governments still exact military service of persons who, being born within their jurisdiction, have become the naturalized citizens of another state. See NATIONALITY; NATURALIZATION.
It has now become the general practice of nations to deliver up fugitive criminals which escape from one state and take refuge in another. This practice of extradition is still based upon treaties between individual nations defining the precise crimes for• the commission of which a fugitive will be de livered up. See EXTRADITION ; ASYLUM ; FU GITIVE FROM JUSTICE.
The needs of international intercourse have given rise to a class of diplomatic agents (q. v.) whose position has now come to in character. These agents are not only the channel of communication be tween the government which sends them and the government to which they are sent, but they are also the personal representatives of their government at the foreign court.
See AMBASSADOR; MINISTER; CHARGE n'AF FAmES.
Treaties are the contracts entered into by states for the purpose of creating special relations between them. Good faith in the observance of these treaties has come to be a recognized principle of international law. When a difficulty arises as to their meaning, practically the same rules of interpretation are applied as those of municipal law in the case of contracts between individuals. See