You can have a general law against monopolies (or near monopolies), e.g. if a company gets 80% of the market share, then the company is regulated. You don't nee

You can have a general law against monopolies (or near monopolies), e.g. if a company gets 80% of the market share, then the company is regulated. You don't need to proactively use regulation to prevent that from happening, because the chances are that the regulation is not necessary and factually speaking decreases competition.