But Roberts challenged the lawyer. "Have there been episodes, egregious episodes of the kind you are talking about in states that are not covered?" the chief justice asked.
Absolutely, Adegbile replied.
"Well, then it doesn't seem to help you make the point that the differential between covered and noncovered continues to be justified," Roberts said.
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, Alaska Natives and Hispanics.
Among the covered states, Alabama, Alaska, Arizona, Georgia, South Carolina, South Dakota and Texas are siding with Shelby County, while California, Mississippi, New York and North Carolina argue that the law should be upheld.
Nearly 250 of the 12,000 state, county and local governments covered by the law have used an escape hatch to get out from under the special oversight by demonstrating that they and smaller places within their borders no longer discriminate in voting. The 10 covered towns in New Hampshire are poised to exit as they await federal court approval for an agreement between the state and the Justice Department.
Thousands more jurisdictions also may be eligible, said voting rights expert Gerry Hebert. But that list probably does not include Shelby County, because one of its cities, Calera, defied the voting rights law in 2008 and provoked intervention by the Justice Department during the Bush administration.
Alabama's statistics offer fodder to both sides.
"I could tell you that in Alabama the number of legislators in the Alabama Legislature are proportionate to the number of black voters. There's a very high registration and turnout of black voters in Alabama," Rein said.
Kagan put forward other numbers showing the state at or near the top of successful claims of voting discrimination. She the state is about 25 percent black but has no black elected statewide official.
Exit polls in November showed Obama won only about 15 percent of the state's white voters. In neighboring Mississippi, the numbers were even smaller, at 10 percent, the surveys found.
The prior approval requirement played a major role last year in blocking or delaying voting laws in South Carolina and Texas.
Federal judges in Washington refused to sign off on two separate Texas plans to institute a tough photo identification law for voters and redistricting plans for the state's congressional delegation and Legislature. Also, South Carolina's plan to put in place its own voter ID law was delayed beyond the 2012 election and then allowed to take effect only after the state carved out an exception for some people who lack photo identification.
Those episodes were not discussed Wednesday, although they are part of the voluminous written filings in the case.
Instead, the bulk of the discussion concerned Congress' actions in 2006, when overwhelming majorities in the Republican-led Congress approved and President George W. Bush signed a 25-year extension of the prior-approval measure, which was first adopted in the Voting Rights Act of 1965.
Scalia pointed to the lopsided vote as a reason to question its legitimacy, even though as Kagan said, every senator in states covered by the law voted for it. Perhaps, he said, they decided "they'd better not vote against it, that there's nothing, that there's none of their interests in voting against it."
Later, Scalia said he worries that the provision will never fade away because members of Congress would be reluctant to risk a vote against it. "It's a concern that this is not the kind of a question you can leave to Congress," he said.
Scalia capped his comment with this observation: "Even the name of it is wonderful: The Voting Rights Act. Who is going to vote against that in the future?"
A decision is expected by late June.
The case is Shelby County, Ala., v. Holder, 12-96.