As the authority of the international judge depends on his integrity,
so also does the universal law arise from, and remain supported by,
the true principles of right and justice; in other words, by the
fundamental distinction between right and wrong. A statute, a despotic
prerogative, and an established principle of common law, rest upon
different sanctions. They may be the causes of the greatest injustice,
may sow the seeds of national ruin, and yet may even require
revolutions for their reformation; but any one of the laws of nations
preserves its vitality, only with the essential truth of its
principles; a change in the feeling of mankind on the great question
of real justice, destroys it, and it simply remains an historical
record of departed opinion, or a point from which to date an advance
or retreat in the career of the human mind.

It is for this reason that International Law has been so differently
defined by writers at various periods.

The Law of Nations is _founded_, I have said, on the general
principles of right and justice, on the broad fundamental distinctions
between right and wrong, or as Montesquieu defines it, "on the
principle that nations ought in time of peace to do each as much good,
and in time of war as little harm as possible." These are the
principles from which any rule must be shown to spring, before it can
be said to be a rule for international guidance. But what are the
principles of right and wrong? These are not left to the individual
reason of the interpreter of the law for the time being, but are to be
decided by the _public opinion of the civilized world_, as it stands
at the time when the case arises.