Lawyers for the Justice Department and Rep. William Jefferson squared off in oral arguments in a federal appeals court Tuesday over the May 2006 FBI raid of the Louisiana Democrat’s Congressional office and the practical challenge created by the protection of legislators inherent in the Constitution’s Speech or Debate Clause.

More specifically, the two sides debated a thorny question: How do you allow a Member of Congress who is under investigation to assert his constitutional privilege without having to essentially seal his office and have the police shadow his every move to prevent the destruction of evidence?

A lawyer for Jefferson argued that the Speech or Debate Clause gives Members an unlimited ability to protect legislative materials from inspection by the executive branch and that the May 2006 raid of the Congressman’s office was unconstitutional. That privilege requires that the lawmaker be allowed to review any documents sought by the executive branch to determine what materials are part of the legislative process.

But the government countered that allowing a Member to screen materials that were sought by the FBI before handing them over would create an unmanageable process under which the lawmaker would be “given the keys to the evidence locker.”

Deputy Solicitor General Michael Dreeben argued for the Justice Department that the search warrant executed by federal agents in Jefferson’s Rayburn Building office a year ago limited the materials taken from the office to nonlegislative matters that may provide evidence of bribery, mail fraud or corrupt practices. Many of these materials also had been part of a subpoena that had been issued to Jefferson, though he apparently had not provided the government with the documents it was seeking, and the search covered a broader universe or documents.

For two years, the FBI has been probing whether Jefferson took improper payments from the telecommunications firm iGate and attempted to bribe public officials in Nigeria and Ghana. The founder of iGate, Vernon Jackson, and Brett Pfeffer, a former Jefferson staffer, have pleaded guilty to bribing the Congressman.

While the amount of material seized during the raid is not public, the three-judge panel and the attorneys described an enormous amount of evidence that was seized. As a result of the legal dispute, most of the material essentially has been in limbo, with the government allowing Jefferson to review documents and choose which ones to assert his Speech or Debate privilege over. The Congressman’s claims of privilege are then reviewable by a judge.

But Robert Trout, Jefferson’s attorney, said this procedure is insufficient to protect the Congressman’s constitutional privilege because the executive branch already has reviewed and removed documents that may be protected by the privilege. While the search team is prohibited from communicating with the prosecution team about the documents they have seen, Trout said that barrier is not sufficient to prevent privileged documents from being used against Jefferson.

“Every single document in the office was reviewed by the executive” branch, he argued.

Chief Judge Douglas Ginsburg cautioned Dreeben that by unilaterally searching files for material that met the terms of the warrant, it appears that “you are reserving for the government the right to say what is and is not privileged.”

But Dreeben countered that the alternative would be an unwieldy process in which a Member of Congress could take months to sort through files and determine what materials to hand over, all the while operating a Congressional office with constant foot traffic in and out. Such a process would create “massive delay” and investigators ultimately would be unable to testify in court to the chain of custody of any particular document.

Dreeben also noted that there has been evidence in the case that Jefferson “during an earlier search was attempting to shield documents” — an apparent reference to an affidavit by an FBI agent that during a raid on Jefferson’s home, the lawmaker was seen slipping documents into a blue bag in his living room, which he knew already had been searched.

Ginsburg pointed out to Trout that the government has “a legitimate interest in ensuring that documents or records are not destroyed” and that the court must be careful not to establish a process “that is completely impractical.” Trout replied that the Justice Department could work out “with House leadership” a process for protecting documents without trampling the Member’s rights, which he said is that kind of “logistical problem that prosecutors and defense lawyers go through every day.”

Jefferson’s legal team is asking the court to declare the search of his office unconstitutional and to order the Justice Department to return all documents and hard drives that were removed from the office during the search.

Also hearing the case alongside Ginsburg were Judge Karen Henderson and Judge Judith Rogers.