Having developed his own branch of the faith, the New Reformed Orthodox Order of the Golden Dawn, during the 1960s, he was also initiated into other traditions, including Gardnerianism and Feri, in subsequent decades.
Alongside this, he was also an important figure in the creation of the Covenant of the Goddess, an organisation designed to protect the civil rights of members of the Wiccan community in the United States.
He has also published academic work studying the early development of Gardnerian Wiccan liturgy, primarily through his controversial 1991 book Crafting the Art of Magic.
[1] Kelly became an organizer and leader in the Neo-Pagan community while studying for a master's degree in creative writing at San Francisco State University in 1967 and 1968.
[1] Shortly after moving to Mill Valley, Kelly experienced what he described as a "spontaneous mystical experience," when a vision of the Goddess first appeared to him at the age of 15.
[4] Although Kelly was raised as a Roman Catholic, his vision of the Goddess in Mill Valley triggered a lifelong interest in alternative religions.
"[4] In 1978, Kelly self-published the memoir Hippie Commie Beatnik Witches: A History of the Craft in California, 1967-77 about the rise of modern American Paganism.
The academic scholar Chas S. Clifton has cited the book as an "invaluable source" for the sociological study of the History of Wicca, particularly insofar as it describes the innate differences between "the more established Anglo-American witches" who claimed lineage-descent from Gerald Gardner and the West Coast Pagans of the 1960s who were working in "the American tradition of self-creation.
He was active in scholarly professional societies, and from 1987 to 1990 co-chaired the steering committee for the American Academy of Religion's Group on New Religious Movements.
To accept Kelly's theory that Gardner "invented" a new religion, would mean giving up the belief that Gardnerian Wicca was the revival of an ancient faith previously held in secret by a few survivors.
Donald H. Frew complained that Crafting the Art of Magic contained errors in quoting source texts to support Kelly's theory.