According to Shelly Muleman, why are the police never able to catch Dusty Muleman and his crew dumping the Coral Queen's waste into the water?

According to Shelly, the water was being polluted by the Coral Queen's sewage. Shelly said that a civilian worker at the Coast Guard station, Billy Babcock, had a gambling addiction and owed a lot of money to Dusty. Instead of repaying him, he was tipping him off every time a complaint was registered against him and an inspection was planned.