"This case is closed. I can't find against you, Snopes, but I can give you advice. Leave this country and don't come back." (13)
The Justice has discretion to exercise his judgment on Abner, even though there isn't enough evidence to hold him accountable for his actions legally.
"Barn burner!" (16)
We know that the speaker of this judgment is "half again [Sarty's] size" (17). In the same way that Sarty believes his father's enemy's are his own, this kid thinks that if a father is a barn burner, the sons must be too.
"You were fixing to tell them. You would have told them." (29)
Since we know that Sarty did plan to lie for his father, we can feel the brutal sting of this injustice. Sarty probably realizes that if he wants his father to think he's a loyal son, he'll have to spend his life proving it to him.