Not sure these are the type of songs you mean but:

Steve Earle has done a number of songs about specific justice issues. He focuses on the death penalty. Some of the titles are Billy Austin & Over Yonder(Jonathon's song). He also did one called Justice in Ontario. It's a great song that covers Ontario's history from the mob killing of the Donnelly family to the biker wars of the late 80's. Just about everything on his last three albums is overtly policitical. Even Copperhead Road is highly political song, but most people just think it's a catchy little tune! The lyrics to pretty much everything he's ever recorded can be found at www.steveearle.net

The Tragically Hip's Wheat Kings is about David Millgard's wrongful conviction--written before he was released from jail. The Hip sing alot of political stuff, if you can translate Gord Downey's rantings!