Obama said the Voting Rights Act, endorsed by wide majorities in Congress, had secured the right to vote for millions of Americans.
"While today's decision is a setback, it doesn't represent the end of our efforts to end voting discrimination. I am calling on Congress to pass legislation to ensure every American has equal access to the polls."
The Court ruled 5-4 that Section 4 of the 1965 law -- a cornerstone of civil rights legislation -- was unconstitutional, calling on Congress to redefine which states must seek government approval for changes to their electoral codes.
The Voting Rights Act -- which was last renewed by Congress in 2006 -- is opposed by some states which see it as outmoded, but a number of civil rights organizations argue it is still needed.
Under the act, nine mainly southern states, as well as local governments in seven states, are required to obtain Justice Department approval for any changes to their voting laws.