Abstract
This paper tackles the notion of the essential security interest of a State as an exception enshrined in numerous treaties since the beginning of the 20th century. The purpose of the analysis is to establish whether the practice of international courts, tribunals, and other bodies competent to settle the disputes under international law has created any guidelines for interpretation of sometimes vague and discretionary terms used in the wording of essential security interest clauses included in different international treaties. The method is based on the exegetical analysis of jurisprudenceof international courts, tribunals and dispute settlement bodies in cases concerning interpretation of essential security interest clauses. The protection of vital interests of the State, designed as an exception to treaty-based international obligations,has been well established in treaty practice. The wordings of particular essential security interest clauses differ depending on the objects and purposes of the particular treaties, but the core stipulations of the essential security interest clauses remain very similar. The analysis of the judgments, awards and decisions allows to formulate some general conclusions as to the application of essential security interest clauses. Measures allowed under essential security interest exception must be intended toprotect ‘essential security interests’ of the invoking State. Although States remain discretion to define their essential security interests, it must be done in good faith, consistent with the ordinary meaning of the stipulation and treaties’ object and purpose.