The Coast Guard will enforce various safety zones for maritime events in the Captain of the Port Northern Great Lakes. Enforcement of these safety zones is necessary to protect the safety of life and property on the navigable waters immediately prior to, during, and immediately after this event. During the period, the Coast Guard will enforce restrictions upon, and control movement of, vessels in a specified area immediately prior to, during, and immediately after events. During each enforcement period, vessels must stay out of the established safety zone and may only enter with permission from the designated representative of the Captain of the Port Northern Great Lakes.
Source: Federal Register USCG
Link: Safety Zones; Recurring Safety Zones in Captain of the Port Northern Great Lakes Zone