The Execution of Catherine Willows - S3-E6
Continuity mistake: At one point Catherine is at the coffee shop and the parents of a murdered girl come to talk to her. She is holding her coffee in the right hand and her cell phone rings and she grabs it with her left. The shot switches angles while Catherine is talking and her cell phone has magically shifted to her right hand.
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.