The rule that anything and everything belonging to the delinquent State may be made the object of reprisals has, however, exceptions; for instance, individuals enjoying the privilege of exterritoriality while abroad, such as heads of States and diplomatic envoys, may not be made the object of reprisals, although this has occasionally been done in practice.[37] In regard to another exception--namely, public debts of such State as intends performing reprisals--unanimity does not exist either in theory or in practice. When Frederick II. of Prussia in 1752, by way of negative reprisals for an alleged injustice of British Prize Courts against Prussian subjects, refused the payment of the Silesian loan due to English creditors, Great Britain, in addition to denying the question that there was at all a just cause for reprisals, maintained that public debts may not be made the object of reprisals. English jurists and others, as, for instance, Vattel (II. § 344), consent to this, but German writers dissent.[38] [Footnote 37: See the case reported in Martens, _Causes Célèbres_, I. p. 35.] [Footnote 38: See Phillimore, III. § 22, in contradistinction to Heffter, § 111, note 5. The case is reported with all its details in Martens, _Causes Célèbres_, II. pp. 97-168. The dispute was settled in 1756--see below, § 437--through Great Britain paying an indemnity of £20,000.] [Sidenote: Positive and Negative Reprisals.] § 38. Reprisals can be positive or negative. One speaks of positive reprisals when such acts are performed as would under ordinary circumstances involve an international delinquency. On the other hand, negative reprisals consist of refusals to perform such acts as are under ordinary circumstances obligatory; when, for instance, the fulfilment of a treaty obligation or the payment of a debt is refused. [Sidenote: Reprisals must be proportionate.] § 39. Reprisals, be they positive or negative, must be in proportion to the wrong done and to the amount of compulsion necessary to get reparation. For instance, a State would not be justified in arresting by way of reprisal thousands of foreign subjects living on its territory whose home State had injured it through a denial of justice to one of its subjects living abroad. But it would in such case be justified in ordering its own Courts to deny justice to all subjects of such foreign State, or in ordering its fleet to seize several vessels sailing under the latter State's flag, or in suspending its commercial treaty with such State. [Sidenote: Embargo.]