The USA asserts a contiguous zone of 24 miles from the coast (along with a number of other countries) which it can control. Was the marked off area within this zone. The Navy REGULARLY holds live fire and tactical exercises off the coast of VA and NC and requires ships and boats to detour arround any announced exercise area. My understanding is that these are within the 24 mile zone as they can be heard directing other ships to divert on land based VHF.
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