Query: What is a law enacted by Congress that states that it refuses to regulate some industries as long as the states have regulations in place already?
Context: In areas like antitrust, trademark, and employment law, there are powerful laws at both the federal and state levels that coexist with each other. In a handful of areas like insurance, Congress has enacted laws expressly refusing to regulate them as long as the states have laws regulating them (see, e.g., the McCarran-Ferguson Act).