McCallum remained with the firm for 28 years, before joining the U.S. Department of Justice in 2001 as Assistant Attorney General for the Civil Division.

In this position, he oversaw litigation involving the defense of challenges to presidential actions and acts of Congress; national security issues; immigration; benefit programs; commercial issues including health care fraud, banking, insurance, patents, debt collection; and the Food Drug and Cosmetic Act.

He served as Acting Deputy Attorney General from September to December 2004 and from August 2005 until he resigned on being nominated as Ambassador to Australia.

One prosecution witness, Matthew Myers, said he was told by Justice lawyers that McCallum wanted him to remove part of his testimony.

In her 2006 decision in the case, Judge Gladys Kessler placed limits on tobacco companies' abilities to market cigarettes, but found that a previous appeals court ruling prevented her (in the judicial branch) from requiring the industry to pay for a smoking cessation program.

"I feel that [from the seminars] I have got a good grounding in the fundamentals of what is going on in a very, very important relationship to the U.S. with Australia, and I'm eager to learn and experience that firsthand", he said.

Following Schieffer's departure to take up the position of Ambassador to Japan in January 2005, the U.S. was represented by a Chargé d'Affaires, Bill Stanton, who also departed Australia before McCallum's appointment.

The long delay was caused by the Bush administration's apparent inability to find a candidate who was suitably close to the President but willing to undergo the scrutiny which accompanies the Senate confirmation process.