This is precisely the place where the USA has difficulty in controlling the Canadian border. It is a combination of remote wilderness area, and maritime border. In the oceans you can have a Coast Guard making sure things are secure. Even the Great Lakes are big enough to use the same techniques. But how do you secure this small lake?
People can walk across the border through the forest with a compass to keep them pointed east. They can float across a wide creek in the northern section. Or they can come across the lake, either in the shallow bay on the west, or the deeper water on the east. And look at the islands in the lake. You can get to a Canadian Island, and at night, wait for the patrol boats to go by and when they move behind an American island, get in canoes and hop that short distance to the American island. There is more than one spot to do this island hop. In the morning a speedboat can come openly to pick up the campers on the island.
And don't blame the Indians on the Red Lake Reserve. Look at Buffalo Bay. A canoe at night can depart Canada, go south across the border over water, and land on the mainland south of the 49th parallel. The thing is that these are relatively short over water trips. Hand paddled canoes can easily do it. A rubber raft or even an air mattress can do it. A clever person will use a partially deflated air mattress so they are submerged in the water, and wear a hat with a piece if a tree branch attached. Any patrol boat will see wood debris in the lake and avoid it.
But don't blame Canada. Maritime borders are almost impossible to seal completely. Smugglers transfer stuff to fishing boats in International waters. The fishing boats head in under the Golden Gate bridge or up the Columbia into a huge uncontrolled coastline. The same goes for all of the Great Lakes coastline. Even the Potomac is not completely controlled. Smugglers do bring stuff in past Norfolk up the river in spite of the military installation.
In some places walls will work. But you still need to understand the networks, the suppliers and the customers, because people will continue to traffic in other ways. If they bring people into Canada, give them fake green cards and let them walk across the border, how does that differ from bringing girls to Haiti, giving them fake passports and flying them in through Atlanta?