This paper attempts to apply Greimas’ s narrative semiotic approach in legal discourse interpretation. To be more specific, it examines different levels of meaning structures—both deep and surface structures—of a legal case report with the aim of demonstrating the logic of legal signification. The surface structure of the case report is examined through the actantial narrative schema and the canonical narrative schema which also helps manifest the transformation of the actant’s modalities in different phases of his/her quest. The narrative logic of case reports as a legal genre can thus be obtained at the end of the analysis. The deep structure of the case report is presented in forms of semiotic square, in which a series of underlying logical implications of the case report is visualized. Furthermore, the study shows that the two levels of meaning structure(surface and deep) are logically consistent and the deep structure underpins the surface one.