May–June 1976 — North Country Anvil, p. 136: “If voting could change anything, it would be illegal; when it threatens to change anything, it becomes illegal.” No author given.
24 September 1976 — a letter to the Lowell, Massachusetts Sun from Robert S. Borden: “If voting could change anything it would be made illegal!”
1979 — the Yale Book of Quotations (2006) files the saying under “Sayings” and cites Rennie Ellis, Australian Graffiti Revisited (1979): “If voting could change things, it would be illegal.”
April 1982 — Mother Jones: “The graffiti that says, ‘If voting changed anything, they’d make it illegal’ just about sums it up.”
1984 — Jonathon Green’s The Cynic’s Lexicon lists the modern wording under GRAFFITI, dated London, 1979.
2007 — Jon Winokur’s The Big Curmudgeon, p. 623, prints it with the byline EMMA GOLDMAN — the first time her name appears beside it in Popik’s file.