Responsible for over 410,000 square miles and 1,340 linear miles of water border with Canada, the Great Lakes Air and Marine Branch conducts air and marine operations that include border security and domain awareness and works with federal, state and local counterparts in providing investigative support, high-risk warrant support, and security for National Special Security Events.
The Great Lakes Air and Marine Branch at Selfridge Air National Guard Base provides primary aviation and marine response capabilities to the Border Patrol's Detroit Sector, which is responsible for securing more than 860 miles of international border between Canada and the U.S.
Air and Marine Operations of U.S. Customs and Border Protection Mission
Each of the nation's border regions provides a nexus point where three transnational threats converge: drug trafficking operations, undocumented alien smuggling and contraband smuggling, and terrorist groups. The border is not merely a physical frontier. Effectively securing it requires attention to processes that begin outside U.S. borders, occur at the border and continue to all interior regions of the U.S. U.S. Customs and Border Protection views the border as a continuum of activities where the physical border is the last line of defense, not the first. Consequently, CBP's strategies address the threats and challenges along the continuum.
AMO's presence on the Northern Region was established August 20, 2004. The Northern Region operating environment differs appreciably from other borders and requires a different law enforcement approach. Northern Region locations were chosen with the strategic goal of providing an efficient and appropriate interdiction/law enforcement response to criminal activity.
The Northern Region is defined as the area between the U.S. and Canada, running from Washington State through Maine, including the Great Lakes region. The terrain, which ranges from densely forested lands on the west and east coasts to open plains in the middle of the country, is comprised of sparsely populated federal, state and tribal lands along the immediate border area.
https://www.cbp.gov/border-security/air-sea/oam-operating-locations