All these rules are, however, subject to the Rule of Reciprocity.  This is thus laid down by Sir William Scott, in the case of the Santa Cruz,

“that at the commencement of a war, it is the constant practice of this country to condemn property seized before the war, if the enemy condemns, and to restore if the enemy restores.  It is a principle sanctioned by that great foundation of the Law of England, Magna Charta itself, which prescribes, that at the commencement of a war the enemy’s merchants shall be kept and treated as our own merchants are treated in their country."[13]

[Sidenote:  Droits of Admiralty.]

[14]In England, at present, however, these liberal principles are modified by Rights of Admiralty, the foregoing rules being applied rather to property upon the land than within the territory; for although, when captures are made in ports, havens, or rivers, within the body of the country of the realm, the Admiralty is in reality excluded, yet Prize Courts have uniformly, without objection, tried all such captures in ports and havens within the realm; as in the case of ships not knowing hostilities, coming in by mistake, before the declaration of war or hostilities; all the ships of the enemy are detained in our ports, to be confiscated as the property of the enemy, if no reciprocal agreement is made.[15]

[Sidenote:  Hostile Embargo.]

This species of reprisal is termed a Hostile Embargo.  It cannot well be distinguished from the practice of seizing property found within the territory upon the declaration of war.  It is undoubtedly against the spirit of modern liberality, and has been but too justly reprobated as destroying that protection to property which the rule of faith and justice gives it, when brought into the country in the course of trade, and in the confidence of peace.

It is not, however, as Wheaton states, peculiar to England, but common to modern Europe, except that England does not, in practice, appear to be influenced by the corresponding conduct of the enemy in that respect.[16]

[Sidenote:  Debts Due to and from an Enemy.]

But with relation to Debts Due to an Enemy, previous to hostilities,
English law follows a wiser principle.

On the outbreak of war between Denmark and this country in 1807, the Danish Government, as a measure of retaliation for the seizure of their ships in our ports, issued an ordinance sequestrating all debts due from Danish to British subjects, causing them to be paid into the Danish Royal Treasury.

The Court of King’s Bench decided that this was not a legal defence to a suit in England for the debt, and that the ordinance was not conformable to the Law to Nations.[17] It was observed by the Court, that the right of confiscating debts (contended for on the authority of Vattel,)[18] was not recognised by Grotius,[19] and was impugned by Puffendorf and others; and that no instance had occurred of the exercise of the right, (except the ordinance in question,) for upwards of a century.  This is undoubtedly the law in England, although it may be doubted if this rule still holds so strongly in the United States.