Strictly, there can be no limitation or restriction of independence, for it is a recognized principle that independence must be absolute and inalienable. In fact, every state voluntarily accepts either formally by treaty or tacitly by practice, many conditions which restrain it in the exercise of its powers. The independence of the state is not thereby violated, since the restraint is exercised by the state itself, and is not an act of external control. The number of these restraints which states voluntarily assume is continually increasing, owing to the closer relations of humanity.
The exercise of the right of independence involves the privilege of making treaties, alliances, contracts, and municipal laws, so far as these do not violate international law or the right of independence as possessed by other states. A state may go to war to maintain its independence. The international rights of a state are in general closely related to the right of independence, and derive force from this relationship.
[§ 39. Balance of Power]
Undoubtedly the idea of establishing a relationship among "neighboring states more or less connected with one another, by virtue of which no one among them can injure the independence or essential rights of another without meeting with effectual resistance on some side and consequently exposing itself to danger"[95] is not a modern idea. Ancient states united to prevent the growth of some neighboring power to such magnitude as would threaten their independence.[96] From the beginning of the modern period of international law, Peace of Westphalia (1648), the idea of maintaining an equilibrium among the powers of Europe has had great influence, and until the latter part of the nineteenth century was regarded as one of the fundamental principles of European international practice. Many treaties aim to preserve this balance among the European powers, and the words "balance" and "equilibrium" often appear.[97] The Treaty of Utrecht in its provision between Spain and Great Britain, July 13, 1713, gives as its object ad firmandam stabiliendamque pacem ac tranquillitatem christiani orbis justo potentiæ equilibro. The idea that independence was to be preserved by some balance of power reappears in successive treaties. This idea of the balance of power has led to most diverse action. Unjust rulers have made it the cloak for action entirely outside the sanction of international law. Many times it has "served as the pretext for a quarrel, and repeatedly made hostilities general which would otherwise have been shut up within a comparatively small area."[98] The feeling that the balance of power was a necessary policy for the preservation of European states, led to the idea that states should be constrained to certain lines of action, which would prevent, in many cases, normal growth. Frequently the independence of a state was violated to anticipate an action which might disturb the European equilibrium. The partitions of Poland show a violation of the principles of international law for the sake of giving equal compensation to the parties to it.
The doctrine of the balance of power is not a principle of international law, but merely a maxim of European political practice pretending to state the means of maintaining the independence of European states.[99]
[§ 40. Monroe Doctrine]
Another maxim of political action is that which has become known as the "Monroe Doctrine." While enunciated by a single state, it had in view the maintenance of the independence of the states of the American continent. For many years after the Revolutionary War the opinion prevailed that Europe viewed with disfavor the growth of the American republic. The Holy Alliance, formed on the downfall of Napoleon, was followed by several congresses of European powers, at one of which, held at Verona in 1822, the subject of helping Spain recover her revolting colonies in America was discussed. This led to the declaration of President Monroe in his message of Dec. 2, 1823, that there should be, (1) no more European colonies on these continents, (2) no extension of the European political system to any portion of this hemisphere, (3) no European interposition in the affairs of the Spanish-American republics. This doctrine has been repeatedly affirmed by the United States, and in some instances very liberally interpreted. It in no way embodies a principle of international law, though the European and other states may regard it as expressing the attitude of the United States upon the points covered, and if desirous of avoiding friction, govern themselves accordingly. If it were a principle of international law, the United States would not be justified in changing its attitude upon the doctrine, but probably it would not be seriously maintained that the United States might not enunciate another policy setting aside the Monroe Doctrine. Reddaway well says, "that it produced its desired effect as an act of policy, but in no way modified the Law of Nations."[100] This doctrine cannot be considered as outlining a principle of non-intervention, as has sometimes been claimed, but it rather announces a policy of intervention on the part of the United States to anticipate intervention by other powers.
The doctrine has always failed of legislative indorsement, and has been strenuously opposed by European powers. That it has been recognized, however, to a certain extent, appears by the course of events.[101] It was recently applied in the case of the intervention by the United States in the dispute over the boundary between Venezuela and British Guiana. Great Britain and the United States settled the difficulty by a submission to arbitration.[102]
[§ 41. Non-intervention]
With the right of independence goes the correlative obligation of non-intervention, i.e. of refraining from all acts that would forcibly limit the freedom of another state. This obligation of non-intervention does not extend to the limitation of acts involving no display or threat of force, as in the case of mediation and arbitration. Nor can it be claimed that the obligation of non-intervention can be urged against measures undertaken by a state to preserve its fundamental right to existence. There is no right of intervention, as has been sometimes argued, though an act of intervention may be sometimes justifiable in itself.[103] Intervention is the attempt of one or more states, by means of force, to coerce another state in its purely state action. The making of an alliance between two may influence a third state in its action, but it cannot be considered an intervention, nor is the tender of friendly offices in the settlement of a dispute to which a state is a party, intervention; but when a state directly interferes with the exercise of the authority in another state or by another state, it constitutes intervention. Intervention may vary greatly in degree and in character, whether it be armed or diplomatic. Each case must be considered separately on its merits, and if in any degree a justifiable measure, it must be on the highest grounds, and the motives of the intervening state must be pure. While it is still necessary to discuss the question of intervention in its various forms, yet, as Hall says: "It is unfortunate that publicists have not laid down broadly and unanimously that no intervention is legal, except for the purpose of self-preservation, unless a breach of the law as between states has taken place, or unless the whole body of civilized states have concurred in authorizing it."[104]