Jurisdiction — High seas — Conception of the high seas and freedom of the sea — Res communis omnium — Artificial island constructed by private individuals just outside territorial waters — Demolition order issued by coastal State — Geneva Convention on the High Seas, 1958 — Geneva Convention on the Territorial Sea and Contiguous Zone, 1958 — Whether creating enforceable rights for individuals to the free use of the high seas — Whether creating duty incumbent upon States to prevent their citizens from interfering with exercise of freedom of the high seas in contiguous zone by other States — Whether such duty also a rule of customary international law — The law of Italy