The feds said Garbin, who is from Hartland, deserves credit for assisting investigators in making cases against the other five men charged in federal court.
Others have also been charged in state court -- 14 people total.
The Detroit News, which first posted the story, reports Garbin helped dismiss the idea that the men arrested were victims of entrapment and the U.S. attorney noted the importance of that.
Garbin testified twice providing details on the plan to take the governor at her vacation home using explosives and more.
His guilty plea came in January and called for a 17-and-a-half-year sentence.