Research in code-switching, undertaken against the backdrop of very negative attitudes towards the concurrent use of two or more languages within the same conversation, has traditionally been geared towards rehabilitating this form of language use. Now that code-switching has been rehabilitated, the research tradition faces an entirely new challenge, namely that of its continued relevance. This book argues that, in order to overcome this challenge, research should aim to describe specific interactional practices involving the use of two or more languages and outlines a methodology for doing so. This chapter illustrates this methodology by means of a specific case study. It describes the language choice practice of translinguistic apposition as observed in written texts in Rwanda. In Rwanda, authors often construct appositive structures in two languages. In turn, this possibility raises a theoretical as well as a practical issue. At the theoretical level language alternation is observed in “highly regulated texts” and, at the practical level, readers are assumed to be competent in all the languages involved. The chapter argues that the first issue does not actually arise as language alternation is oriented to as deviance and the second is resolved by reference to notion of ascribed linguistic competence in context.