MBB meaning in Governmental ?

The Montgomery bus boycott was a political and social protest campaign against the policy of racial segregation on the public transit system of Montgomery, Alabama. It was a foundational event in the civil rights movement in the United States. The campaign lasted from December 5, 1955—the Monday after Rosa Parks, an African-American woman, was arrested for her refusal to surrender her seat to a white person—to December 20, 1956, when the federal ruling Browder v. Gayle took effect, and led to a United States Supreme Court decision that declared the Alabama and Montgomery laws that segregated buses were unconstitutional.