The constitutionality of a key part of the nation’s Voting Rights Act appeared in serious trouble in the U.S. Supreme Court on Wednesday as the justices heard arguments over Congress’ 2006 reauthorization of the act.

In Shelby County, Alabama v. Holder, the court is asked whether Congress exceeded its authority under the 15th and 14th Amendments when it re-authorized Section 5 under a formula that the challengers contend is outdated and intrusive on state sovereignty. Section 5 currently requires nine states, including Georgia, and parts of seven others to have any changes in their voting practices pre-cleared by the U.S. Department of Justice or the federal district court in Washington, D.C.

While a large crowd rallied in support of the act on the sidewalk in front of the court, intense questioning ensued inside the courtroom.

Based on the justices’ questions and comments, there seemed to be a clear ideological divide on the answer to Shelby County’s question, with four justices on the conservative side of the bench voicing major misgivings about Section 5 and four on the liberal side defending the power of Congress to make decisions on where the Act should be targeted. Justice Clarence Thomas remained silent, although in a 2009 Voting Rights Act challenge, he wrote he would find Section 5 unconstitutional.

"This is a question of renewing a statute that we know has worked," said Justice Stephen Breyer to Shelby County’s counsel, Bert Rein of Wiley Rein. He added that if there was an "old disease that had gotten a lot better, but was still there, wouldn’t you want to keep the remedy going?"

The old disease at which the act was targeted—tools and devices of discrimination—was cured, responded Rein, but the formula for detecting states and localities engaged in new forms of voting discrimination has not been updated and is an inappropriate vehicle for making that determination.

Justice Samuel Alito Jr. asked Solicitor General Donald Verrilli Jr., "When [Congress] reauthorized the act in 2006, why wasn’t it incumbent on Congress to make a new determination of coverage using a formula based on up-to-date statistics?"

Verrilli defended Congress’ 15,000 page-record of findings that discrimination was most persistent in the covered jurisdictions, and that the Section 4(b) formula was justified under any test the court would impose.

Justice Antonin Scalia noted that when Section 5 was adopted in 1965, there was double-digit opposition to it in the Senate and with each reauthorization, the number of opposing votes decreased until there was no Senate opposition in 2006.

"I think that’s attributable to a phenomenon that has been called the perpetuation of racial entitlements," he told Verrilli. "Once you enact them, it’s very hard to get out. I’m fairly confident this will be re-enacted in perpetuity" unless a court steps in to examine the justification. "The concern here is this is not the kind of question you can leave to Congress."

Verrilli said it would be "extraordinary" to look behind the judgment of Congress in "a sort of motive analysis." He added, "These are predictive judgments about human behavior and voting that Congress knows much about." And the Constitution, he said, expressly gives Congress the enforcement power in this area.

Chief Justice John Roberts Jr. asked Verrilli whether the Obama administration thinks Southerners "are more racist than citizens in the North."

Verrilli said no.

The question, and others like it from the conservative justices, largely echoed the doubts they first expressed four years ago in a similar case that ended without resolving the constitutionality of the 2006 renewal of the voting rights law.

While the justices and lawyers uniformly praised the effectiveness of the advance approval requirement since it took effect in 1965, Justice Anthony Kennedy said the country passed other important laws that also ran their course. "Times change," he said.

If Kennedy sides with his four more conservative colleagues, there would be a five-justice majority to cut back on the law or get rid of it entirely.

As his administration was defending the voting rights law, President Barack Obama was across the street unveiling a statue of civil rights pioneer Rosa Parks, who in 1955 famously refused to give up her seat on a city bus in Montgomery, Ala., to a white man. The court will have to decide whether the conditions that gave rise to that seminal event are, like the statue, a part of history, or whether they persist in parts of the nation.

The court’s four liberal justices appeared uniformly to be willing to defer to the decision by Congress that more progress needs to be made before freeing states from the special federal monitoring.

Justice Sonia Sotomayor acknowledged some parts of the South had changed, but asserted that recent voting rights lawsuits in Alabama suggested that Shelby County, near Birmingham, has not made sufficient progress.

"Why would we vote in favor of your county whose enforcement record is the epitome of the reasons that cause this law to be passed in the first place?" Sotomayor asked Rein.

Justice Elena Kagan chimed in that any formula devised by Congress "would capture Alabama."

In court papers, Rein argued that "dire local conditions" that once justified strict federal oversight of elections no longer exist.

In a friend-of-the court brief, Georgia is siding with Shelby County.