The US has a federal database on who has what prescription. Doctor shopping is illegal. Florida pain clinics have managed to stay legal because they are real doctors with a real license and they give out legal prescriptions. Bad thing is that they give out these prescriptions to anyone that will pay. This is de facto, so it's hard for police to get anyone on it. It's only since wide media attention and documentaries such as the one shown on the show Vanguard that police have started to investigate, especially when those who own the clinic are usually ex-convicts.