Founded in 1925 in Toronto, the Canadian Labour Defense League was arguably the Communist Party of Canada’s most effective front organization. The central aim of the CLDL was the protection of strikers from prosecution. By 1927 fifty-two groups were associated with the CLDL, with a combined membership exceeding 3000 people. In 1930, the organization had expanded to an affiliated membership of 123 associations and 5000 individuals members; in 1933, membership increased to 17 000 and 350 branches of the CLDL operated across Canada. The CLDL achieved prominence during the worst years of the depression by “promoting communist policies, agitating on behalf of the CPC and defending in courts over six thousand individuals who had ventured astray of the law because of their militant labour activities.” It was also dedicated to removing Section 97 from the Criminal Code and the recent amendment to the Immigration Act designed to stamp out political radicals in Canada in the wake of the Winnipeg General Strike in 1919. The trial of the eight leaders leaders of thh Communist Party of Canada in the 1930s under Section 97 represented the high point of activity for the group; members of the CLDL raised $160 000 in bail money for the accused, organized rallies and demonstrations, and put together a massive petition with over 459 000 signatures calling for the repeal of Section 97.
The CLDL became moribund in the late 1930s and the federal government formally banned the organization in 1940 in the midst of attempts to revive the group during the war. Soon after the ban, A.E. Smith, founder and president of the CLDL, created the National Council for Democratic Rights in 1941 to lobby against the wartime ban on the CPC. Instead of defending the rights of all Canadians, however, the efforts of the CLDL and its successor were limited to “workers and those on the political left ... did not pretend to follow the dictum of making no distinctions about whose liberties [it] defended.” (see Petryshyn)