The general rule (Article 31 — the interpretive charter): a treaty shall be interpreted (1) ingood faith; (2) according to the ordinary meaning of the terms; (3) in their context; and (4) in the light of the treaty's object and purpose — the integrated rule (not a hierarchy of steps but a single combined operation); with the context including the text, preamble, annexes, and related agreements/instruments (Article 31(2)); and subsequent practice and subsequent
agreements as authentic interpretation's living elements (Article 31(3)) — the special meaning rule (31(4): the parties' special usage prevails over ordinary meaning).
Supplementary means (Article 32 — where the travaux live):travaux préparatoires (the negotiating history — the preparatory works: drafts, records, committee reports) and the circumstances of conclusion — to confirm the Article 31 result, or where that result is ambiguous/manifestly absurd/unreasonable. The doctrine's politics: the textualists (the object-and-purpose school of the ICJ's early years) vs. the intention-seekers (the travaux school) — Article 32's placement of travaux as supplementary marks the textualist victory, but the ICJ uses travaux freely in confirmation (Gabčíkovo, Kasikili/Sedudu; LaGrand and Avena's execution-order debates).
The interpretive maxims (the supplementary toolkit):effet utile (effectiveness — the interpretation giving the provision meaning); lex specialis derogat legi generali; harmonious reading of the whole treaty; interpretation contra proferentem (rare); the presumptions (no intention to breach international law — the VCLT-friendly presumption; no derogation from sovereignty without clear words).