This paper examines linguistic behaviour, particularly the illocutionary forces in convention formulation discourses. It scratches across pragmatics and law, the illocutionary act and a specific register of legal manuscripts. Illocution is a dimension of speech act theory that positions the intention inherent in spoken or written utterances. For a lengthy investigation, a couple of other discursive variables are supplementary. One is mood, a concept borrowed from Halliday's systemic functional linguistics, which upholds three types of mood in the English language: declarative for statement, imperative for command and interrogative for question. Further is the speech act type. Based on Searle's classification, they are assertive, constitutive, representative, directive and expressive.