Public intervention in the banking sector takes three main forms: prudential regulation, especially with the Basel II ratio for adequacy of a bank's own funds for their exposure to risk ; insuring deposits, the goal of which is to ensure a minimum level of protection for depositors and savers in order to avoid a run on banks ; and control and supervision of banks by public authorities, which ensures that the rules are applied properly. Intervention by central banks, through their monetary policy and as lenders of last resort, constitutes the fourth means of regulating the banking system, and the main form of intervention in financial markets. Central banks intervene in order to ensure the stability of financial systems. The financial crisis has shown that traditional modes of public intervention in the financial system are ineffective and insufficient. Before analyzing the principles and limits of these forms of public intervention, we examine cases of exceptional intervention and support to banks by public powers during the crisis. Then, in conclusion, we compare these forms of public intervention with the current state of financial systems.
