Hart-Scott-Rodino
The US law requiring large mergers to be notified before closing.
The Hart-Scott-Rodino Antitrust Improvements Act of 1976 requires parties to transactions above an annually adjusted size threshold to notify the Federal Trade Commission and the Department of Justice and then wait before closing, normally thirty days.
If the agencies want more, they issue a second request, a demand for documents and data that is expensive enough to deter marginal deals on its own. The agency that reviews a given deal is decided between the two by a clearance process: the Federal Trade Commission takes most food, drink and consumer goods, the Department of Justice takes beer and spirits.