Canadian Bacon is back on the menu, but not without studio squabbles du jour. The John Candy political satire, directed by Michael Moore (Roger & Me) and financed by PolyGram's Propaganda Films, was originally slated for a fall '94 release from distributor MGM. But then, according to Moore, PolyGram decided to keep the film for its own studio, Gramercy Pictures. From there the rumors started flying: The $12 million Bacon had tested poorly, there weren't enough Uncle Buck-style Candy high jinks, and the film would go straight to video. ''MGM and PolyGram had their blowout with me in the middle,'' says Moore, whose Bacon will premiere at the Cannes Film Festival on May 25. ''Here I am reading that it's going straight to video, and it's going straight to Cannes!'' Canadian Bacon, which was the second-to-last film Candy made before his death (but will be his last new film released), will open Stateside on Sept. 29.