He was a member of the Progressive Conservative Party, and served as a cabinet minister in the governments of William Davis and Frank Miller.
[5] He served as a backbench supporter of Davis's government for the next four years, and lost to Liberal candidate Marvin Shore by 2,282 votes in the 1975 election.
[6] Walker was returned to the legislature in the 1977 election for London South, defeating Liberal incumbent John Ferris by 2,211 votes.
On June 6, 1983 he changed cabinet positions becoming the Provincial Secretary of Justice, a position he held until February 1985 at which time he became the Minister of Consumer and Commercial Relations in the Cabinet of Premier Frank Miller, who had succeeded Premier Bill Davis as leader of Progressive Conservative Party.
[9] Walker was a prominent figure on the right-wing of the Progressive Conservative Party, and developed an organization for a future leadership bid in the early 1980s.
[11] In the period 1993 until 2003, Walker was chief fundraiser for Mike Harris, Leader of the PC Party in Ontario, and Premier from 1995 until 2003.
[12] Walker's legal practise took him to Toronto where from 1985 until 1998 he was Counsel to Toronto law firms of Holden, Murdoch and Finlay (later Holden Day Wilson), and latterly Miller Thompson; as well as being Honorary Counsel to Walker and Wood, a firm he started in London, Ontario.
[14] From 1992 until 1995 Walker was Canadian commissioner on the International Joint Commission, a treaty organization between Canada and the United States affecting issues of water quality and water quantity on the 330 lakes, rivers and streams across the common border, including the Great Lakes.
He left the firm in July 2005, shortly after describing Black's ongoing legal difficulties as a "soap opera".