Merger is a financial tool that is used for enhancing long-term profitability by expanding their operations. Mergers occur when the merging companies have their mutual consent as different from acquisitions, which can take the form of a hostile takeover.
The business laws in US vary across states and hence the companies have limited options to protect themselves from hostile takeovers. One way a company can protect itself from hostile takeovers is by planning shareholders rights, which is alternatively known as - poison pill. If we trace back to history, it is observed that very few mergers have actually added to the share value of the acquiring company. Corporate mergers may promote monopolistic practices by reducing costs, taxes etc.
Such activities may go against public welfare. Hence mergers are regulated d supervised by the government, for instance, in US any merger required\s the prior approval of the Federal Trade Commission and the Department of Justice. In US regulation son mergers began with the Sherman Act in 1890.