In this paper, we address two questions concerning negative imperatives in Korean: (i) what is the morpho-syntactic nature of ma1 in negative imperatives?; and (ii) why is it impossible to form negative imperatives with short negation an? We will argue that the clause structure of imperatives include a projection of deontic modality and a projection of imperative operator encoding illocutionary force, and that ma1 is a lexicalization of long negation and deontic modality. We then propose that a negative imperative with short negation is ruled out because such construction maps onto incoherent interpretation which can be spelled out as I direct you to bring about a negative state or a negative event.