Field Director Charles White of the National Association for the Advancement of Colored People (NAACP) speaks at a podium outside the U.S. Supreme Court building on June 25, 2013 in Washington, DC.

A deeply divided Supreme Court on Tuesday halted enforcement of the federal government's most potent tool to stop voting discrimination over the past half century, saying it does not reflect racial progress.

In a 5-4 ruling, the court declared unconstitutional a provision of the landmark Voting Rights Act that determines which states and localities must get Washington's approval for proposed election changes.