This qualitative in-depth case study explores the influence of financial regulation on risk control within Banque de Montagne, a large listed bank in Sweden. Specifically, the purpose of this paper is to investigate the impact of the European Banking Authority´s Guidelines on Internal Governance (GL 44), through Swedish Financial Regulation FFFS 2014:1, on the bank’s risk organization along the three lines of defense model of internal control. FFFS 2014:1 requires banks to reform risk control structures, processes, and roles through a mandated split between the operational risk and compliance functions of the internal risk organization. Through an analysis of 41 interviews, more than 2100 pages of internal and external documents, and over 200 hours of observations from 2015 to 2017, the research identifies the relevant changes to transparency and accountability mechanisms across the three lines of defense within the organization. The operationalization of these concepts through risk control mechanisms is an important consideration for both banks and regulators who rely on the three lines of defense model as an industry-wide adoption for effective risk control. The findings suggest that whilst intra- and inter-organizational accountability mechanisms have strengthened under the changed organizational structure through the implementation of FFFS 2014:1, challenges to effective transparency remain and may have ambiguous consequences for both organizational and regulatory aims.