Territory — Boundaries — Tacit agreement — Unilateral recognition — Continuous, effective and uncontested exercise of sovereignty — Critical date — Natural frontiers — Watershed line

Sources of international law — Protest and acquiescence — Estoppel — Acquiescence in boundary dispute

States — Federal States and confederations — Application of international law in dispute between two States within a confederation — Boundary dispute between two Swiss cantons

Relationship of international law and municipal law — Customary international law — Application of international law in disputes between Swiss cantons — The law of Switzerland