The paper analyzes the rules concerning the decision to adopt defensive tactics in the face of a hostile bid, set forth by the Consolidated Act on Financial Markets and Intermediares. The regulation presents and enabling aspect in that it does not set ex ante the level of resistance that firms can implement. Rather, it merely sets a proresistance policy that suits their needs. At the same time, the law recognizes that agency costs may plague the decision concerning whether or not to adopt defensive tactics. The law, therefore, introduces a procedural mandatory requirement of shareholders' approval for all decision that may obstruct a hostile takeover. The paper posits that this regime strikes an overall efficient equilibrium in the trade-off between the costs and benefits generated by resistance. Finally, a tentative "public choice" history of the evolution of defensive tactics regulation in Italy is attempted. The picture that emerges appears to confirm the prediction that unitary systems tend to produce more efficient takeover regulation than federal systems.