James Morgan (25), inset, had been stopped by gardai in Dublin city centre who found a Stanley blade in his bag.
He was charged with possession of a weapon, but explained he had been using the blade to carve cardboard templates to teach children a "quicker" way to create graffiti. Dublin District Court heard Morgan had run the graffiti seminars for youngsters in Dublin.
Morgan, of Whitestown Green, Mulhuddart, had pleaded not guilty to possession of a weapon at Pearse Street Garda Station on March 20 last.
Morgan's solicitor explained that the artist had had the blade for cutting templates from cardboard.
Judge Bryan Smyth dismissed the charge.