This article presents an account of the cross-linguistic variation in the availability of negative imperatives. By imperatives, I refer to sentences with a distinctive imperative morphology on the main verb and/or a distinctive syntax. In many languages (e.g., Italian, Modern Greek, and Spanish), imperatives cannot be negated. Instead, negative commands are expressed with negative subjunctives and/or infinitivals. However, in German, French, English, Bulgarian and Serbo-Croatian, imperatives can be negated. I argue that some languages rule out negative imperatives because the syntax of the language derives a structure which maps onto an incoherent interpretive representation. The analysis I propose builds on the intuition that the directive force contributed by the imperative mood cannot be negated. The negative imperative Don't call! means I require that you not call; it does not mean I do not require that you call. This judgment was already noted by Frege, consequently positing that illocutionary force operators cannot be negated. Pursuing this idea further, I propose that negative imperatives are unavailable in some languages because the syntax derives a structure in which the operator encoding directive force arrives within the c-command domain of negation, where it is interpreted as being negated. As this is incoherent, the structure is ruled impossible. The proposed analysis has implications for the mapping between syntax and semantics of imperatives in particular. In general, it provides evidence that the set of available syntactic structures in a language is restricted by uniform mechanisms for semantic interpretation across languages.