In 1904, he was appointed a puisne judge of the Supreme Court of British Columbia. In 1906, he was appointed a justice of the Supreme Court of Canada. On January 14, 1919, he was appointed to the Privy Council of the United Kingdom.[5] Duff was the first and only Puisne Justice of the Supreme Court of Canada to be appointed to the Imperial Privy Council. In 1924, he was elected as an honorary bencher of Gray's Inn, at the recommendation of Lord Birkenhead.[6]
Duff also heard more than eighty appeals on the Judicial Committee of the Privy Council, mostly Canadian appeals; however, he never heard Privy Council appeals from the Supreme Court of Canada while he served on the latter, otherwise, it would have been seen as a conflict of interest. The last Privy Council appeal heard by Duff was the 1946 Reference Re Persons of Japanese Race.[6]
In 1942, Duff served as the sole member of a Royal Commission constituted to examine the Liberal government's conduct in relation to the defence of Hong Kong. The resulting report, which completely exonerated the government, proved to be controversial, and was seen by many as a whitewash.[citation needed]
Upon reaching the mandatory retirement age for judges in 1939, his term of office was extended by three years by a special Act of Parliament;[8] in 1943, his term of office was extended for another year by Parliament.[9][6] He retired as Chief Justice in 1944.[citation needed]
Duff employed a conservative form of statutory interpretation. In a 1935 Supreme Court of Canada judgment, he detailed how judges should interpret statutes:
The judicial function in considering and applying statutes is one of interpretation and interpretation alone. The duty of the court in every case is loyally to endeavour to ascertain the intention of the legislature; and to ascertain that intention by reading and interpreting the language which the legislature itself has selected for the purpose of expressing it.[10]
Duff has been called a "master of trenchant and incisive English," who "wrote his opinions in a style which bears comparison with Holmes or Birkenhead."[11] A former assistant of Duff, Kenneth Campbell, argued that Duff was "frequently ranked as the equal of Justices Holmes and Brandeis of the United States Supreme Court".[12]Gerald Le Dain, an academic and later a judge on the Supreme Court, asserted that Duff "is generally considered to have been one of Canada's greatest judges."[13] Other writers have taken a less favourable view, instead arguing that Duff's reputation is largely unearned; his biographer concluded that he was not an original thinker, but essentially a "talented student and exponent of the law rather than a creator of it."[14]
apparent that he has given certain factors very little consideration in formulating his decisions. ... In constitutional cases, not only are the actual facts of the case significant but the surrounding social, economic and political facts are equally significant. A shift in these latter factors is as important in deciding a case as any other change in the facts. It is this consideration that Chief Justice Duff ignored.[16]
