§3. On the other hand, a State that has admitted aliens is bound not only to abstain from injuring them through the operations of its government, but also to take due care to prevent its members from injuring them, so long as they are within its territory; and, where prevention has failed, to inflict punishment and provide reparation for any wrongs that they may have suffered. And, similarly, it is at all times the duty of a State to take reasonable care to prevent the inception within its territory of acts injurious to other States or their members intended to take effect outside its territory. Nor can the extent of this obligation, I conceive, depend on the internal constitution or condition of any country, at least so far as the duty of reparation goes. It may be admitted that a State is not ``bound to alter the form of polity under which it chooses to live, in order to give the highest possible protection to the interests of foreign States''; but if it prefers a polity that renders it more dangerous to others, it must take the risk of having to give more compensation for damage done to their interests. Other nations, on the principle of mutual non-interference, have no right to interfere with its constitution and laws, so long as its foreign obligations are tolerably fulfilled; but, correspondingly, it has no right to make them an excuse for non-fulfilment.
A precise general definition of ``reasonable care'' can hardly be given; but it may be laid down that ``somewhat more forethought in prevention of noxious acts is due during war'' or internal disturbance in neighbouring countries, than in time of peace.
This duty of control, of course, extends to the case of the aliens to whom a State gives hospitality. It must take reasonable care to prevent them from doing mischief to its neighbours. This duty becomes important through the natural tendency of the law-breakers of any community to fly to neighbouring countries to escape punishment. Generally speaking, such law-breakers are likely to be mischievous where they take refuge, and it is the common interest of both the States concerned that they should be handed over for trial and punishment in the country whose laws they have broken. But there is likely to be some margin of disagreement between two States as to the kinds of acts that deserve punishment; and we cannot say broadly that every State is bound to accept any other State's definition of crime, and hand over for punishment persons whom it believes to be innocent. Its clear duty is only not to facilitate in any way the performance of future acts that it admits to be mischievous. It is, indeed, conceivable that the mischief caused to a State by its neighbour's encouragement to law-breakers may be sufficiently grave to justify complaint, or even, in the last resort, forcible suppression: but such serious results are hardly likely to follow from any disagreement as to the definition of ordinary crime, if the neighbour is a civilised State in which order is tolerably maintained.
The chief practical difficulty arises in the case of what are called ``political'' offenders---that is, persons who have violated the laws of their country by acts designed to effect a change in its constitution. According to the principle of non-interference no State should do anything calculated to prevent (or cause) internal changes in another: and it would seem that the surrender of political offenders is an interference of this kind on behalf of the existing government. It is, indeed, undeniable that such attempts, when made without adequate cause or reasonable prospect of success, may be mischievous in the highest degree: but a State cannot generally be expected to undertake the responsibility of deciding how far any particular attempt at a revolution in a foreign State was justifiable. On the other hand, by affording a refuge to escaped rebels after an unsuccessful attempt at revolution, it undoubtedly renders revolutionary enterprises somewhat less perilous to those who engage in them, and so far may be said to interfere on the side of revolution. In this difficulty, the best compromise would seem to be, that a foreign State should not surrender fugitives whose alleged crime does not involve any wrong to private individuals,---or any damage to the community, other than what necessarily attends interference with governmental functions; and that it should not even be bound to surrender them, even if they are accused of acts involving such wrong or damage, provided these acts were merely normal incidents in an attempt at revolution: but that, if it does not surrender them, it should be bound to take special care that they do not use its territory as a basis for carrying on serious hostilities against their government,---by placing them if necessary under special control or supervision, and expelling them if there is adequate evidence that they have thus abused its hospitality. Should it refuse to take either of these latter courses when occasion arises, it must be held responsible for any mischiefs that the fugitives may succeed in inflicting on their own State.
The right of each State to exclude foreigners must extend, in strictness, even to ambassadors or other agents of communication between States; a refusal to receive them cannot be held to justify war. But it is obviously most expedient, with a view to the maintenance of friendly relations between States, that such agents should not only be admitted, but received with special marks of courtesy; and even that special immunities from the jurisdiction of the foreign country in which they temporarily reside should be granted them---partly from considerations of courtesy, partly to secure the independence of action which the functions of these officials require.