Sanders was a founding member and the second president of the Vancover-based Association for Social Knowledge, Canada's first lesbian and gay rights organisation; he was actively involved in getting homosexuality decriminalized in Canada.

In 1991 he cofounded the Lesbian and Gay Immigration Task Force. The following year, representing the International Lesbian and Gay Association (ILGA), he was the first "out" person to speack at the United Nations, in the annual session of the Sub-Commission on Prevention of Discrimination and Protection of Minorities. In 1997, he played a central role in redrafting ILGA's constitution, and was elected to its Board.

Sanders began teaching law in 1969, first in Ontario and then at the University of British Colombia. In 1990, he began teaching a course on lesbian and gay legal issues there, this being one of the first such law courses in the country.