In a democracy, what type of government regulations help to maintain free market capitalism?

I don’t believe that democracy can truly exist in a system that protects or exalts the interests of one group above another. The goal of a democracy, in my opinion, is not the equality of condition, but the equality of rights.

Given that no system can be free from the influence of one group or another, what place does the government have in ensuring that free market competition exists within a capitalist economy? What regulations are improper? And why?