§ 217. Several writers[432] speak of non-hostile relations between belligerents created by licences to trade granted by a belligerent to enemy subjects either within certain limits or generally. It has been explained above, in § 101, that it is for Municipal Law to determine whether or not through the outbreak of war all trade and the like is prohibited between the subjects of belligerents. If the Municipal Law of one or both belligerents does contain such a prohibition, it is of course within the discretion of one or both of them to grant exceptional licences to trade to their own or the other belligerent's subjects, and such licences naturally include certain privileges. Thus, for instance, if a belligerent allows enemy subjects to trade with his own subjects, enemy merchantmen engaged in such trade are exempt from capture and appropriation by the grantor. Yet it is not International Law which creates this exemption, but the very licence to trade granted by the belligerent and revocable at any moment; and no non-hostile international relations between the belligerents themselves originate from such licences. The matter would be different if, either in time of peace for the time of war, or, during war, the belligerents agreed to allow certain trade between their subjects; but non-hostile relations originating from such an agreement would not be relations arising from a licence to trade, but from a cartel.[433] [Footnote 432: See, for instance, Hall, § 196; Halleck, II. pp. 343-363; Lawrence, § 214; Manning, p. 168; Taylor, § 512; Wheaton, §§ 409-410; Fiore, III. No. 1500; Pradier-Fodéré, VII. No. 2938.] [Footnote 433: See below, § 224.] II PASSPORTS, SAFE-CONDUCTS, SAFEGUARDS Grotius, III. c. 21, §§ 14-22--Vattel, III. §§ 265-277--Hall, §§ 191 and 195--Lawrence, § 213--Phillimore, III. §§ 98-102--Halleck, II. pp. 323-328--Taylor, § 511--Wheaton, § 408--Moore, VII. §§ 1158-1159--Bluntschli, §§ 675-678--Heffter, § 142--Lueder in Holtzendorff, IV. pp. 525-527--Ullmann, § 185--Bonfils, Nos. 1246-1247--Despagnet, Nos. 558-561--Pradier-Fodéré, VII. Nos. 2884, 2932-2938--Nys, III. pp. 504-505--Calvo, IV. §§ 2413-2418--Fiore, III. No. 1499, and Code, Nos. 1742-1749--Longuet, §§ 142-143--Mérignhac, pp. 239-240--Pillet, pp. 359-360--_Kriegsbrauch_, p. 41--Holland, _War_, No. 101--_Land Warfare_, §§ 326-337. [Sidenote: Passports and Safe-conducts.]