unlawful.]

One of the most immediate consequences of the outbreak of hostilities
is the complete interruption of Commercial Intercourse between the
subjects of the countries at war, even to the extent of holding it
unlawful, after war has begun, except under special licence of the
government, to send a vessel to the enemy's country to bring home,
with _their permission_, one's own property, when war has broken out.

There cannot exist at the same time a war for arms and a peace for
commerce; from the very nature of war all commercial intercourse
ceases between enemies. This interdiction of intercourse is the result
of the mere operation of war; for declarations of war generally enjoin
on every subject the duty of attack on the subjects of the hostile
state, of seizing their goods, and doing them every harm in their
power.[20]

From the very nature of war itself, all commercial intercourse ceases
between enemies. The utility, however, of merchants, and the mutual
wants of nations, have almost got the better of the law of war as to
commerce. Hence, commerce is alternately permitted and forbidden in
time of war, as princes think it most for the interest of their
subjects. A commercial nation is anxious to trade, and accommodate the
laws of war to the greater or lesser want that it may have for the
goods of the other. Thus sometimes a mutual commerce is permitted
generally; sometimes as to certain merchandizes only, while others are
prohibited; and sometimes it is prohibited altogether. In this manner
there is partly peace and partly war, between subjects of both
countries.[21]