The provision was a huge success, and Congress periodically has renewed it over the years. The most recent occasion was in 2006, when a Republican-led Congress overwhelmingly approved and President George W. Bush signed a 25-year extension.
The requirement currently applies to the states of Alabama, Alaska, Arizona, Georgia, Louisiana, Mississippi, South Carolina, Texas and Virginia. It also covers certain counties in California, Florida, New York, North Carolina and South Dakota, and some local jurisdictions in Michigan and New Hampshire. Coverage has been triggered by past discrimination not only against blacks, but also against American Indians, Asian-Americans, Alaskan Natives and Hispanics.
Before these locations can change their voting rules, they must get approval either from the U.S. Justice Department's civil rights division or from the federal district court in Washington that the new rules won't discriminate.
Congress compiled a 15,000-page record and documented hundreds of instances of apparent voting discrimination in the states covered by the law dating to 1982, the last time it had been extended.
Six of the affected states, Alabama, Arizona, Georgia, South Carolina, South Dakota and Texas, are backing Shelby County's appeal.
In 2009, Roberts indicated the court was troubled about the ongoing need for a law in the face of dramatically improved conditions, including increased minority voter registration and turnout rates. Roberts attributed part of the change to the law itself. "Past success alone, however, is not adequate justification to retain the preclearance requirements," he said.
Jurisdictions required to obtain preclearance were chosen based on whether they had a test restricting the opportunity to register or vote and whether they had a voter registration or turnout rate below 50 percent.
A divided panel of federal appeals court judges in Washington said that the age of the information being used is less important than whether it helps identify jurisdictions with the worst discrimination problems.
Shelby County, a well-to-do, mostly white bedroom community near Birmingham, adopted Roberts' arguments in its effort to have the voting rights provision declared unconstitutional.
Yet just a few years earlier, a town of nearly 12,000 people in Shelby County defied the voting rights law and prompted the intervention of the Bush Justice Department.
Ernest Montgomery won election as the only black member of the five-person Calera City Council in 2004 in a district that was almost 71 percent black. The city redrew its district lines in 2006 after new subdivisions and retail developments sprang up in the area Montgomery represented, and the change left his district with a population that was only 23 percent black.
Running against a white opponent in the now mostly white district, Montgomery narrowly lost a re-election bid in 2008. The Justice Department invalidated the election result because the city had failed to obtain advance approval of the new districts.
The case is Shelby County v. Holder, 12-96.