Sovereign immunity — Foreign States — Arbitration within framework of Convention on the Settlement of Investment Disputes between States and Nationals of other States, 1965 — Arbitral award of compensation against State in favour of foreign company — Enforcement of award — Article 54 of the Convention — Simplified procedure for obtaining an exequatur — Article 55 of the Convention — Preservation of immunity from execution of foreign States — Whether an order granting an exequatur constitutes a measure of execution — The law of France