The US Supreme Court has struck down a key part of a landmark Civil Rights-era law designed to protect minority voters.

The Supreme Court ruled on Tuesday that a key provision of the Voting Rights Act cannot be enforced unless Congress comes up with an up-to-date formula for deciding which states and localities still need federal monitoring.

Ruling effectively puts an end to the requirement that has been used, mainly in the South, to open up polling places to minority voters in the nearly half century since it was first enacted in 1965, at a time when it was not unusual for blacks in some parts of the country to be essentially barred from voting.

Al Jazeera's Tom Ackerman, reporting from Washington, said the impact of this ruling is unclear but the question is whether localities will be free to engage discrimination against 'non-white' voters.

This ruling is a defeat for civil rights groups who think that kind of safeguard is needed to prevent discrimination, our correspondent said.

The law  was put in place to ensure that states with deep history of racial discrimination did not prevent minorities from their constitutional right to vote.

Obama 'disappointed'

The jury said in 5-4 vote that the law Congress most recently renewed in 2006 relies on 40-year-old data that does not reflect racial progress and changes in US society.

The court, however, did not strike down the advance approval requirement of the law that has been used, mainly in the South, to open up polling places to minority voters.

The jury did say that lawmakers must update the formula for determining which parts of the country must seek Washington's approval, in advance, for election changes.

US President Barack Obama has said that he was deeply disappointed with Supreme Court decision.

Stating that voting discrimination in the US still exists, Obama said the high court's ruling is a setback but that efforts to end voting discrimination will continue.

Obama quickly called on Congress to pass a new law to ensure equal access to voting polls for all.

The decision comes five months after Obama, the nation's first black chief executive, started his second term in the White House, re-elected by a diverse coalition of voters.

Source: Al Jazeera and agencies