You didn't need a centralized regulatory agency to enforce a law. Even federal laws, if they're written so, can be prosecuted by individual states or even individual persons. Some aspects of antitrust law already work this way.

Doing so can prevent regulatory capture and shelter enforcement from the vicissitudes of politics. It also doesn't require maintaining a government workforce. OTOH, you have to be careful what you ask for. Unless a law is very narrowly tailored then ubiquitous enforcement can have it's own problems, e.g. CEQA.