The aim of the given study is to examine the use of inserted clauses in the legal discourse and their unique role in this speech genre.  The investigation of the topic is conducted in line with the principles of Functional Discourse Grammar. In the course of analysis we apply the theory of speech acts, namely performatives, the fundamental tenets of which permit to view the specific combination of shall+inserted clause as a particular feature of legal discourse.  These overcomplicated grammatical structures are shown to fulfill the immediate function of performatives, that of enacting legal acts and doing things in the pragmatic sense of word, to the full extent.