Grissom's Divine Comedy - S8-E12
Continuity mistake: When Warrick demands to see the hands of a suspect, the suspect refuses and Warrick pushes him up against a wall. During which time, there are multiple angles which show Warrick wearing sunglasses, then suddenly not wearing them anymore. (00:23:30)
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.