That Montgomery Bus Boycott was based on the principle of blank

The Montgomery Bus Boycott was an event for civil rights. Buses used to be segregated. The whites sat in front and the blacks in the back. Rosa Parks, a colored person, was sitting in the back and refused to move to the back because she was tired. She was forcefully moved from her seat and arrested. Black people all over the South started to sit in the front and refused to move after this incident. They eventually were forcefully moved off the bus and a few were arrested.

The answer on Edgenuit y is "nonviolent resistance"