Going off the reservation is a common expression (despite it being politically incorrect today). It can mean to engage in disruptive activity outside normal bounds. Originally, "going off the reservation" literally meant leaving the reservation to which one is restricted. This article is about the phrase and its usage, including this one: More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.