Wickard v. Filburn started it. It took the DEA operating under the authority established by that ruling to create the "Task Force" operations that train, direct, and in some cases pay the salaries of local cops involved in these operations. They set the example for the rest.
Ever wonder why hardly any prominent citizens are ever tied to 'the business' of drugs? Someone always knows who's moving quantity. It has to come in by air, ship or truck. Mena, Arkansas comes to mind.