This article is an analysis of the claim that a universal ban on certain (‘anti-markedness’) grammars is necessary in order to explain their nonoccurrence in the languages of the world. Such a claim is based on the following assumptions: that phonological typology shows a highly asymmetric distribution, and that such a distribution cannot possibly arise ‘naturally’—that is, without a universal grammar-based restriction of the learner's hypothesis space. Attempting to test this claim reveals a number of open issues in linguistic theory. In the first place, there exist critical aspects of synchronic theory that are not specified explicitly enough to implement computationally. Second, there remain many aspects of linguistic competence, language acquisition, sound change, and even typology that are still unknown. It is not currently possible, therefore, to reach a definitive conclusion about the necessity, or lack thereof, of an innate substantive grammar module. This article thus serves two main functions: acting both as a pointer to the areas of phonological theory that require further development, especially at the overlap between traditionally separate subdomains, and as a template for the type of argumentation required to defend or attack claims about phonological universals.