Capitalism is inseparable from a free market system. They are in fact the same thing and have been regarded as such for a century across all the writings of every modern proponent of free market economics. From Hayek to Mises to Friedman.

To the extent you have regulation, is the extent to which you lack a Capitalist economy. All systems opposite to Capitalism make use of extreme State control of the economy through various regulatory means. Whether we're talking rudimentary Socialism or its derivatives, including Fascism and Communism. It's an inversion. You can either have market-based economic levers or you can have State levers, or you can mix them and get a mixed economy to the extent you do so. Regulation is antithesis to Capitalism because it imposes State control over the economy. The more regulation you add, the less market freedom you must inherently have; the regulation removes possible action and decision making by free actors in the economy, it places those decisions into the hands of the State (ie out of the bounds of Capitalism to dictate).