States as international persons — Sovereignty and independence — In foreign relations — Request for mutual assistance by foreign State — European Convention on mutual assistance in criminal matters, 1959 — Seizure of strong box by municipal authorities — Alleged violation of Articles 2 & 5 of Convention — Vacation of seizure by municipal courts — Appeal by foreign State — Whether foreign State entitled to bring appeal — Whether foreign State acting iure imperii or iure gestionis — The law of Switzerland