Their allusion was doubtless to the _International_ (L.R.3 A.and E.321), which is irrelevant to the present enquiry.

The question is a new one, but, though covered by no precedent, I cannot doubt that it is covered by certain well-established principles of international law, which, it is hardly necessary to remark, is no cut-and-dried system but a body of rules founded upon, and moving with, the public opinion of nations.
That branch of international law which deals with the relations of neutrals and belligerents is, of course, a compromise between what Grotius calls the "belli rigor" and the "commerciorum libertas." The terms of the compromise, originally suggested partly by equity, partly by national interest, have been varied and re-defined, from time to time, with reference to the same considerations.

It is perhaps reasonable that, in settling these terms, preponderant weight should have been given to the requirements of belligerents, engaged possibly in a life-and-death struggle.

"Ius commerciorum aequum est," says Gentili; "at hoc aequius, tuendae salutis." There is accordingly no doubt that in land warfare a belligerent may not only interrupt communications by road, railway, post, or telegraph without giving any ground of complaint to neutrals who may be thereby inconvenienced, but may also lay hands on such neutral property--shipping, railway carriages, or telegraphic plant--as may be essential to the conduct of his operations, making use of and even destroying it, subject only to a duty to compensate the owners.

This he does in pursuance of the well-known "droit d'angarie," an extreme application of which occurred in 1871, when certain British colliers were sunk in the Seine by the Prussians in order to prevent the passage of French gunboats up the river.