On June 1, 2009, the U.S. government will implement the full requirements of the land and sea phase of Western Hemisphere Travel Initiative. The proposed rules require most U.S. citizens entering the United States at sea or land ports of entry to have a passport, passport card, or WHTI-compliant document.
See the Department of Homeland Security's GetYouHome.gov for more information on the changing travel requirements.
This is a US government law, but I'm sure Canada will be checking too just to be sure you can get back into the US after your Ignace Outposts fishing trip.
