"Only this court can resolve this important question," the Justice Department wrote in its 28-page appeal, filed Wednesday. "Until it does so, investigations of corruption in the nation's capital and elsewhere will be seriously and perhaps even fatally stymied."

Jefferson's attorney, Robert P. Trout, declined comment Friday.

The Constitution prohibits the executive branch from using its law enforcement powers to interfere with the lawmaking process, and the FBI should have given Jefferson a chance to argue that some of the documents involved legislative business, according to the August ruling by the U.S. Court of Appeals for the District of Columbia Circuit.

The May 2006 raid was part of a 16-month international bribery investigation of Jefferson, a nine-term Democrat from New Orleans. He is accused of accepting $100,000 from a telecommunications businessman, $90,000 of which was later recovered in a freezer in the congressman's Washington home.

Jefferson pleaded not guilty in June to charges of soliciting more than $500,000 in bribes while using his office to broker business deals in Africa.

In its August ruling, the federal appeals court held that the raid itself was constitutional. But it ordered the Justice Department to return any legislative documents it seized from Jefferson's office on Capitol Hill. Still undecided is whether prosecutors can use other records it confiscated as part of their bribery case against Jefferson.

Justice Department attorneys said the ruling "fundamentally misinterprets" constitutional guarantees that allow the executive branch to investigate and prosecute corruption in Congress.

"Although this case involves a search of a Capitol Hill office (a concededly extraordinary event), the court's decision threatens to impede searches of Members' homes, vehicles, or briefcases," government attorneys wrote in their appeal to the Supreme Court.

In addition to Jefferson, the Justice Department is investigating disgraced lobbyist Jack Abramoff's dealings with Reps. John Doolittle and Jerry Lewis, both California Republicans; former Rep. Tom DeLay, R-Texas; and former Sen. Conrad Burns, R-Mont. A dozen people — including former Rep. Bob Ney, R-Ohio, former Deputy Interior Secretary Steven Griles and former White House official David Safavian — have been convicted in the Abramoff probe.

In a Thursday hearing on the Jefferson case, an FBI agent testified that investigators had information about potentially shady business deals involving Jefferson going back the late 1990s. During a pretrial hearing in federal court in suburban Virginia, FBI agent Timothy Thibault said he found a bureau document from the late 1990s questioning Jefferson's business deals with a sugar company.

The IRS is auditing similar issues for 2004 through 2006, the package delivery company said in the filing with the U.S. Securities and Exchange Commission.

"Given the preliminary status of this matter, we cannot yet determine the amount or a reasonable range of potential loss. However, we do not believe that any loss is probable," Fedex said in the filing.

The International Brotherhood of Teamsters, which has asserted FedEx Ground workers are in fact employees and which is campaigning to unionize FedEx Ground drivers, welcomed the IRS decision.

"It's game over for FedEx's independent contractor scam," union President Jim Hoffa said in a statement.

The union said penalties against FedEx could eventually top $1 billion, since the current penalty only covers the year 2002.

FedEx said that it has "strong defenses to the IRS's tentative assessment and will vigorously defend" its position that FedEx Ground's owner-operators are independent contractors.

The filing came a day after Memphis, Tenn.-based FedEx warned that it faces "increase regulatory and legal uncertainty" over the independent contractor model it uses at FedEx Ground, which could result in higher costs..

FedEx Ground uses 15,000 drivers who are paid as independent contractors. Under this system, FedEx Ground drivers can own multiple routes, employing other drivers to deliver packages. Investors like the model because it helps FedEx save money and compete against main rival United Parcel Service Inc and its unionized work force.

The IRS is auditing similar issues for 2004 through 2006, the package delivery company said in the filing with the U.S. Securities and Exchange Commission.

"Given the preliminary status of this matter, we cannot yet determine the amount or a reasonable range of potential loss. However, we do not believe that any loss is probable," Fedex said in the filing.

The International Brotherhood of Teamsters, which has asserted FedEx Ground workers are in fact employees and which is campaigning to unionize FedEx Ground drivers, welcomed the IRS decision.

"It's game over for FedEx's independent contractor scam," union President Jim Hoffa said in a statement.

The union said penalties against FedEx could eventually top $1 billion, since the current penalty only covers the year 2002.

FedEx said that it has "strong defenses to the IRS's tentative assessment and will vigorously defend" its position that FedEx Ground's owner-operators are independent contractors.

The filing came a day after Memphis, Tenn.-based FedEx warned that it faces "increase regulatory and legal uncertainty" over the independent contractor model it uses at FedEx Ground, which could result in higher costs..

FedEx Ground uses 15,000 drivers who are paid as independent contractors. Under this system, FedEx Ground drivers can own multiple routes, employing other drivers to deliver packages. Investors like the model because it helps FedEx save money and compete against main rival United Parcel Service Inc and its unionized work force.