State territory — In general — Acquisition of territorial sovereignty — Occupation — Prescription — Acts of sovereignty as basis for claim to sovereignty in derogation of title established by treaty — Effective, notorious and peaceful possession — Possession in good faith and animus domini — Principle of uti possidetis — Plots of frontier land — Boundary Convention between Belgium and the Netherlands, 1843 — Subsequent acts by Netherlands authorities — Relevance of routine and administrative nature of acts — Relevance of absence of protest by Belgium Government.

Treaties — Operation of — Conditions of validity of — Mistake — Effect of — Whether affecting validity of treaty as a whole or only of provision containing error — Burden of proof — Evidence required — Effect of express proviso relating to errors — Comparison of texts of documents relating to same subject — matter — Possibility of error in copying — Relevance of intention of Parties to treaty — Relevance of surrounding circumstances — Effect of failure to challenge relevant treaty provision by Party now seeking to plead mistake — Relevance of length of time treaty in existence and unchallenged — Effect of uncertainty and unresolved discrepancy — Effective and peaceful possession of dispute territory as supplementary evidence of mistake — Boundary Convention, 1843, between Belgium and the Netherlands.

Treaties — Conclusion of — Ratification — Effect of unratified treaty — Treaty ceding land — Whether evidence that title to land is in ceding State — Effect of admission made in course of negotiation.

Treaties — Interpretation of — Rules of — Boundary Convention — Examination of minutes of boundary commission — Belgian — Netherlands Boundary Convention, 1843.

Treaties — Special kinds of — Boundary Convention — Interpretation of — Mixed Boundary Commission set up by Convention — Authority of Commission to delimit territory — Effect of resolution of Commission — Reference in Boundary Convention to earlier Treaty between same Parties — Two Treaties read together — Common intention of Parties — Boundary Convention between Belgium and the Netherlands, 1834 — Treaty of London determining boundaries between Belgium and the Netherlands, 1839.

Arbitration — Evidence — Documentary evidence — Communal Minute in nature of treaty — Effect of non — production of copy by one Party — Authority of only existing copy — Discrepancy between texts of two Minutes — Original text and transcribed text — Which must prevail.

Disputes — Negotiation — Proposals made in course of — No agreement reached — Evidentiary value of proposals in later dispute between same Parties — Admission made during negotiations — Whether Party making admission may later challenge it.

State territory — Parts of — Boundaries — Land boundaries — Determination of — Enclosed areas — Operation of boundary convention — Principle of uti possidetis — Relevance of maps — Examination of work of boundary commission — Belgian-Netherlands Boundary Convention, 1843.