The U.S. Supreme Court on Tuesday effectively neutered a vital enforcement mechanism of the 1965 federal law protecting minorities' right to vote.

By a 5 to 4 vote, the high court ruled that Congress must revise the criteria determining which states must obtain federal approval to change their voting laws.

The criteria are set in Section 4 of the 1965 Voting Rights Act and provide the basis of the federal "preclearance" authority established by Section 5.

The current Section 4 standards, as specified in Congress' 2006 reauthorization of the Act, make Alabama, Alaska, Arizona, Georgia, Louisiana, Mississippi, South Carolina, Texas and Virginia subject to preclearance.

Portions of six other states are also subject to federal preclearance.

"Congress did not use the record it compiled to shape a coverage formula grounded in current conditions," Chief Justice John Roberts wrote for the court majority. "It instead re-enacted a formula based on 40-year-old facts having no logical relationship to the present day."

According to the Supreme Court, it is Congress that must now find a new formula to determine which states and portions of states require a close watch on their electoral procedures.

The case developed from a suit brought by Shelby County, Alabama.

Civil rights groups have insisted that the high court should leave Sections 4 and 5 intact as vital tools to protect minority voting rights.

Initially conceived to fight the situation of blacks in the South, in the 1970s the Act was amended to cover Hispanic citizens in Texas, Arizona and areas of California, Florida and New York as well. EFE