The European Central Bank strives to harmonize over 160 national options and discretions (O&Ds) that contribute to the fragmentation of banking union’s regulatory framework. National authorities seem prepared to accept it, despite previously insisting on the inclusion of all O&Ds into the EU legislation. We analyze a sample of O&D choices and their correspondence to cleavages pertinent to the political economy of EU banking. We find that the 11 post-communist member states use O&Ds more stringently to protect capital and liquidity in the local subsidiaries of foreign-own banks, which may complicate their potential opt-in to the banking union.