Convergence or divergence in respect of the OECD Model of tax treaties is achieved at the level of individual treaties concluded by countries through the adoption of provisions that are, or are not, based on the OECD Model. This convergence or divergence can also be achieved through law in action, and specifically through judicial decisions or administrative guidelines which may be ‘inspired by’ or ‘refer to’ the OECD Commentary. In particular, interpretive solutions or principles advanced by the OECD Commentary can be considered by national judges in the application and interpretation of specific treaties. This chapter focuses on how this occurs, proposing a model in which OECD interpretive solutions or principles circulate through ‘judicial transplants’ activated by domestic courts.