Continuity mistake: In the scene where Nick and Sara discover the brother they are looking for is dead, the froth in his mouth changes between shots and in one shot he has no froth in his mouth.
Continuity mistake: In the scene where Jules whacks the slot machine, you see a small dent up close, but in the next shot the wheel is badly damaged. When you see Jules move to the table, the wheel is not damaged at all.
Continuity mistake: In the scene where Sara is talking to Avery while he is packing his bag, you see him wrapping the headphones around his iPod and putting them in the bag, but in the next shot he puts them in his bag again.
Answer: He doesn't have the authority to arrest him - when anyone is arrested in the show, a police officer does it. Also he tells Ty that he is going to be submitting his case findings to Ty's insurance company, who would no doubt contact the IRS, who then would have him arrested for fraud etc.