One of his most influential academic contributions was a seven-pagearticle in the American Economic Review entitled "National BordersMatter." The article has spawned an ongoing international debate on whether tradewithin a nation state is greater than trade among nations, ascompared with the predictions of standard economic models.

As McGill University’s Dean of Arts, McCallum secured a $10 million contributionfrom Charles Bronfman for the establishment of the McGill Institutefor the Study of Canada.

He also participated in the national unity debates of the early 1990s,editing the Canada Round Series of the C. D. Howe Institute and engagingin debate with then Opposition Leader Jacques Parizeau at Quebec'sNational Assembly.

McCallum was the Royal Bank of Canada’s chief economist for six years. Whileconsistently achieving the highest media coverage of bank chiefeconomists, he also engaged in social issues, notably a 1997 Royal Bankconference designed to align the business community with therecommendations of the 1996 Report on the Royal Commission on AboriginalPeoples. The tenth anniversary of his paper at that conference, "TheCost of Doing Nothing," was recently highlighted in Aboriginal Times Magazine.

Backbencher and social issues

McCallum successfully nominated Nelson Mandela as the second honorarycitizen in Canadian history.

McCallum was quite vocal in Canada's debate on Same-Sex marriage. He told the Edmonton Sun in August 2003, "If people want to do something and it doesn’t hurt other people, doesn’t reduce other people’s rights, we should let them do it. Why not?" He also significantly contributed to the final debate before the vote on same-sex marriage on 21 March 2005 saying:

I believe we should always seek to expand the rights of our fellow citizens as long as we do not thereby reduce the rights of others. We should seek to ensure that no group is denied full participation in society. As members of Parliament, we should not ask the question, why should we extend this right? Rather our question should be, why should we not extend the right? Let the burden of proof be on those who wish to limit fundamental rights....Many Canadians will want to accept both of these principles: protect the traditional definition of marriage and protect the rights of minorities. The essence of my message today is that we cannot do both. We cannot have it both ways. We must make a choice between traditional marriage and the protection of minority rights.

Defence Minister

As Defence Minister, McCallum achieved what was then the largestincrease in the annual defence budget ($1 billion) in more than adecade in return for offering up $200 million in savings from reducinglow priority spending. He alsoretroactively reversed a gross inequity which awarded up to $250,000 tomilitary personnel who lost their eyesight or a limb while on activeservice - but only to those with the rank of colonel or above. Now allCanadian Forces members are covered by the plan regardless of rank. Working with Germany, hesuccessfully persuaded NATO to take control over the security mission inKabul, Afghanistan, while also ensuring that the mission was led byCanada. He also determined that the army, rather than the navy or air force, was to be the top priority inbudget allocations.

He became widely known and criticized in 2002 when he admitted, while serving as the Minister of National Defence, that he had never heard of the 1942 Dieppe raid, a fateful and nationally significant operation for Canadian Forces during the Second World War. Ironically, he wrote a letter to the editor of the National Post in response, but committed a further gaffe, confusing Canadian participation in the 1917 Battle of Vimy Ridge in France with Vichy France from 1940 to 1944. Response at the continued historical ignorance prompted outrage and humour among the press.

In November 2002, while still serving as Defence Minister, McCallum encountered further controversy when officials refused to allow him to board an Air Canada flight because his breath smelt heavily of alcohol. McCallum announced soon thereafter that the incident prompted him to abstain completely from alcohol consumption. He reportedly also intended to lose weight and give up smoking.

In January 2003, McCallum prompted both indignation and gales of laughter in the House of Commons when he mocked Conservative MP Elsie Wayne's flamboyant attire. When asked by Wayne about proper identification markers for Canadian military vehicles (to prevent friendly fire incidents), McCallum responded: "if our soldiers were to wear the dress of the honourable member over there, they would be very well identified." McCallum later apologized both inside and outside the House of Commons for using inappropriate language, blaming the excitement of the moment.

Veterans Affairs Minister

McCallum introduced a new charter for younger, postwar veterans who havebeen physically or mentally injured while serving in the CanadianForces. This charter, which became law in 2005, is modeled on the rangeof services provided for returning veterans after World War II.

Expenditure Review Committee

As Chair of Expenditure Review Committee, McCallum achieved expenditurereductions of $11 billion over five years.

He is married to Nancy Lim and has three sons.