Josh, it's from the album "Pine Ridge. an Open Letter to Allan Rock", a compilation Greg Keelor put together to raise money and awareness for the Leonard Peltier Defense Committee. It came out in 1996. Jim did write the song. Greg wrote the song "Pine Ridge", also on the album. Sarah McLachlan, Jane Siberry, Bob Wiseman, the Skydiggers, Ashley MacIsaac, Molly Johnson, John Borra, Change of Heart, and others contributed songs.
Leonard has been imprisoned since 1976 for the alleged killing of two FBI agents on the Pine Ridge Reserve in South Dakota. It's a long and complicated story, but to put it in a nutshell, in the 70s the American Indian Movement (AIM) were standing up to the injustices against the native people. Leonard was one of the leaders. He got "pinned" for these murders when the FBI couldn't pin it on anyone else.
If you want to know more about Leonard, I highly recommend the book, "In the Spirit of Crazy Horse" by Peter Matthiessen, or try to rent the movie, "Incident at Oglala" (1991), a documentary produced by Robert Redford.
You can't buy the album anywhere now. It's been out of print for a long time. I was told that Warner destroyed about 5,000 copies, because of "copyright issues".