It is illegal to launch a water craft from US soil below Niagara Falls, which is the only realistic place to put-in from what I understand. There is a way around this however, you can launch from one of the jet-boats upstream of the rapids legally. Wilderness Tours runs these jet boats, which also runs rafting and kayaking programs on the Ottawa River. The owner of Wilderness Tours allowed his son, Joel Kolawski, and some of friends, the Jackson Clan, to launch off one of their boats. I doubt he would do it for anyone else.