In this paper I argue, on the basis of intuitional and psycholinguistic evidence, that a grammatical constraint on scope ambiguity found in Dutch and some other languages, but not in English, is a rule of pragmatic competence. After showing that this constraint cannot be derived from the obligatory specificity of indefinites in certain contexts, nor from core syntactic properties of Dutch that distinguish it from English, I present experimental evidence that the Dutch scope constraint is not fully acquired by Dutch monolingual speakers until after the age of 12. Given standard assumptions about L1A, this can only be the case if this constraint does not derive purely from UG. I propose a construction-based account of it and suggest that this is generated by the same general cognitive processes that are primarily responsible for adult L2A.