The immunity from execution of a diplomatic agent was a rule long established in customary international law. It derived from the diplomat’s inviolability of person, residence, and property as well as from his immunity from civil jurisdiction. Insofar as it was ever treated in practice or by the writers as a matter separate from immunity from civil jurisdiction, this was usually in the context of the rule (now set out in Article 32.4) that waiver of immunity from jurisdiction does not imply waiver of immunity in respect of execution.
What was not clear in customary international law was the extent to which an automatic exception to immunity from jurisdiction (such as that in respect of private immovable property) necessarily implied an exception to immunity from execution if judgment were given against a diplomat. The Rapporteur to the International Law Commission originally provided that a diplomatic agent should, without any exception, be immune from measures of execution. But the Commission in 1957, after a short discussion substituted the provision which now forms Article 31.3.1 This provision, while safeguarding the inviolability of the diplomat’s person and residence, carries the exception to immunity set out in Article 31.1 to a logical conclusion by permitting judgments given in these cases to be executed. If, for example, the diplomat loses a case relating to title or possession of immovable property the judgment may be enforced, provided that the property in question is not at the relevant time the private residence of the diplomat. Neither he nor any member of his family References(p. 320) may be evicted. If he loses a case relating to a professional or commercial activity, execution would in practice probably be levied first on goods in the receiving State relating to that activity. But in fact the Convention permits execution under these circumstances against any of his property provided that it is not on his person, in his residence, or on the premises of the mission or any other inviolable premises. In practice, therefore, the possibilities of execution of a judgment against a diplomat are limited.
It is, however, most improbable that a diplomat against whom a judgment was given by a court in the receiving State would not voluntarily comply with its terms. If non-compliance with a final judgment of a national court were drawn to the attention of the Ministry of Foreign Affairs of the receiving State, a more serious view would be taken of such an obvious failure to comply with the law than of a refusal by the sending State to waive immunity from jurisdiction. The matter would be drawn to the attention of the government of the diplomat’s sending State and unless some satisfactory explanation were given it is likely that withdrawal of the offending diplomat would be requested.