It's called canon.That's irrelevant.
Why is it irrelevant? You're impeaching Tom Paris because prior to Caretaker he was in prison. Prior to Caretaker, Chakotay was a terrorist and *possibly* a deserter...
If they tell us he wasn't a deserter and resigned his position then it's been fact the whole time we've know him. Even after Caretaker, Tom Paris is in field commiission as part of his work release agreement with Janeway.
Actually he's not, as Janeway says, after Tom helped Voyager track down the Maquis ship, he's cut loose...so in essence at the end of Caretaker, Janeway cuts Tom loose as far as the work release agreement goes and then commissions him as a Lieutenant and makes him Helmsman. He's served his time by that point.