The criminal was convicted by a Native American court and sentenced to 5 months. The court could not sentence more than 12 months. Then the US government got into the act, so technically two different nations, same crime.
Not quite. The conviction was in a special federal court that administers triable law where there is no tribal court. The second trial was in a federal district court. The prosecutor was the same in both cases and elements of the crime were the same in each case. Basically, the same federal prosecuted prosecuted the same person for the same crime in a federal court.