Does macroprudential regulation spillover to foreign financial systems through inter-bank linkages? This question has received a lot of attention in recent years given the discord between the international nature of the global financial system and its regulation and supervision by national jurisdictions (e.g. this article). For example, subsidiaries of Spanish banks issue almost half of all credit issued by commercial banks in Mexico. These subsidiaries are also fully owned by their parent banks headquartered in Spain. Therefore, it is quite natural to ask whether macroprudential regulations in Spain can have unintended consequences on the Mexican financial system and the Mexican economy in general. While Mexican subsidiaries of Spanish banks are de-jure ring-fenced from regulations in Spain, does this hold de-facto?