This paper examines the alternate use of Arabic and English in the context of a university classroom, where a policy to use the former language in place of the latter was being implemented. Analysis of a sample of recorded university lectures of English and Arabic medium classes in sciences and humanities reveals that teachers use code switching, consciously and/or unconsciously, as a pedagogic resource and strategy to achieve a variety of communicative functions, including effective classroom interaction, topic change, and solidarity, among other functions. Hastiness in policy implementation without adequate planning or preparation also seemed to play a role in the translation of policy into actual classroom practice. (Contains 5 notes.)