Unneutral service differs from the carriage of contraband, particularly in being hostile in its nature and involving a participation in the contest. Such service involves assistance in the performance of warlike acts. While the destination is a question of vital importance in the case of contraband, the intent of the act is a matter of highest importance in cases of unneutral service.
The acts generally regarded as in the category of unneutral service are:—
1. The carriage of enemy dispatches.
2. The carriage of certain belligerent persons.
3. Aid by auxiliary coal, repair, supply, or transport ships.
4. Knowing coöperation in the transmission of certain messages and information to the belligerent.
(1) Of the carriage of dispatches, in the case of the Atalanta, Lord Stowell said:—
"How is the intercourse between the mother country and the colonies kept up in the time of peace? By ships of war or by packets in the service of the state. If a war intervenes, and the other belligerent prevails to interrupt that communication, any person stepping in to lend himself to effect the same purpose, under the privilege of an ostensible neutral character, does in fact place himself in the service of the enemy state."[451]
"A neutral vessel carrying hostile dispatches, when sailing as a dispatch vessel practically in the service of the enemy, is liable to seizure. Mail steamers under neutral flags carrying dispatches in the regular and customary manner, either as a part of their mail in their mail bags, or separately as a matter of accommodation and without special arrangement or remuneration, are not liable to seizure and should not be detained, except upon clear grounds of suspicion of a violation of the laws of war with respect to contraband, blockade, or unneutral service, in which case the mail bags must be forwarded with seals unbroken."[452]
Regular diplomatic and consular correspondence is not regarded as hostile unless there is some special reason for such belief.
(2) The limitation in regard to the carriage of certain belligerent persons applies to those who travel in such manner as to make it evident that they travel in the military or naval service of the belligerent state. If the carriage of the person or persons is paid by the state, or is done under state contract, it is regarded as sufficient evidence of unneutral service.[453] The neutral carrier engaged in ordinary service is not obliged to investigate the character of persons who take passage in the usual way. The case of the Trent had no particular bearing upon this subject, as it merely emphasized an already settled principle "that a public ship, though of a nation at war, cannot take persons out of a neutral vessel at sea, whatever may be the claim of her government on those persons."[454]