For the passage in the wikipedia diagram, both of the two paths after the first bifurcation (moving westward) pass through channels less than 24 nautical miles

For the passage in the wikipedia diagram, both of the two paths after the first bifurcation (moving westward) pass through channels less than 24 nautical miles wide. Canada would need to build observation towers but it could be defended with "cannons" e.g. the M777.