Borderline medical products have continued to pose as a challenge to regulators of cosmetics, medical devices and pharmaceutical products in Europe. Borderline products refer to products that exhibit multiple product characteristics and therefore could potentially straddle a minimum of two product regulatory categories. Legislation solutions in the form of the ‘rule of doubt’ provisions function on the principle of adoption of a higher burden in case of confusion exist. Although they do provide immediate solutions, they fail in ensuring legal certainty to all the principal stakeholders. This article discusses the jurisprudence on borderline products based on national and European case law. While this jurisprudence clarifies several regulatory points of conflict, it is in many ways limited. Questions of regulatory categorization are essentially science questions – that are evolving – and are therefore bound to escape determinative categories propounded within European regulations. The solution lies in appreciating the role played by deliberative institutional networks that are active contributors of regulatory disciplines and ensuring mechanisms by which judges will be able to access scientific knowledge on this issue.