Transnational spillovers of systemic risks show that financial regulation is not simply a sovereign power, it also shall be responsible to other states and individuals. Regulatory cooperation is necessary to ensure responsibility. Current arrangements dealing with the financial crisis mainly focus on technical problems, and ignore the accountability mechanism of financial regulation. Such arrangements cannot effectively regulate systemic risks in the long run. This paper argues that accountable financial regulation and its legalization is an essential part of solutions to systemic risks, and suggests the ways to legalize accountable financial regulation.