You are correct in your observation that the event of 1798 does not constitute an element-force of arms/right of conquest- of Belize’s legal arguments to title under international law. The significance of the event is that it represents the last attempt by Spain to assert control over territory it had permitted for usufruct purposes to the British, first to the Belize River, then to the Sibun. The issues of uninterrupted and effective occupation, recognized by the ICJ Statute 38(1) as customary international law, are substantially more important for Belize’s legal arguments, as are those for validity as a boundary delimitation treaty of the 1859 Boundary Convention, and the right of the Belizean people to self-determination. The fact is that the Guatemalan Captaincy General never occupied or exercised any administrative control over the geopolitical space now known as Belize. The records show that this was the purview of the Yucatan Captaincy General under whose administration the space fell.
You are therefore right to conclude that the treaties of 1802 and 1814 have no direct bearing on or implications for the case save as historical indicators of the dynamics of European wars to the extent they pertained to their colonies and territorial imperatives.
Guatemalan historiography on the issue includes a repertoire of legal luminaries: Herrarte -the Great White Book, Orellana- Study of the Special Agreement, to name the more significant ones; who have adhered to a consistent thread of arguments formulated on ex aequo et bono/non legal principles, effectively, perhaps inadvertently, jettisoned on their signature with Belize of the 2008 Special Agreement.
On the other hand, Guatemala has consistently ignored the writings of one legal scholar, the American jurist Manley Ottmer Hudson who, in 1950, at their request provided them with a detailed, well-researched legal opinion, which advised that Guatemala has no valid claim legal, or otherwise-ex aequo et bono, to any part of the territory of British Honduras. In the course of its deliberations the ICJ relies on publications and writings of notable professionals and international jurists. It can be expected that in the raft of arguments in its counter- memorial to the ICJ, if the matter is heard by the Court, Belize will bring into the light of legal scrutiny, this key piece of evidence that Guatemala has chosen to suppress.
Centre for Strategic Studies, Policy Analysis & Research (CSSPAR)