The first period extended until the American Civil War and the Reconstruction era, the second period spanned the nadir of American race relations period until the early 20th century, and the last period began with World War II and the Civil Rights Movement, which led to the repeal of racial segregation laws. Racial legislation has been intertwined with immigration laws, which sometimes included specific provisions against particular nationalities or ethnicities, such as the Chinese Exclusion Act and the 1923 "United States v. Bhagat Singh Thind" case in the US Supreme Court. Race remains an active area of contention with police killings disproportionate to the racial distribution of the US population; Whites are under-represented and Blacks are over-represented.