hayes practiced law until being appointed national executive director of the canadian jewish congress in 1940, a post he would hold until 1959. from 1959 to 1974, he was national executive vice-president. he was also executive director of the united jewish relief agencies of canada from 1938 to 1942. he had spearheaded the community's effort to have immigration restrictions relaxed during and after world war ii and served on a myriad of committees, especially those devoted to human rights.