Caddies are governed by a strict set of regulations on the PGA Tour, as detailed in the official 2024 PGA Tour player handbook, and "players shall be responsible for the conduct and behaviour of their caddies during tournaments."
One of the things caddies can't do on the PGA Tour is get fined, however. The players are responsible for their caddies, so any fine falls on them. For example, the PGA Tour rulebook states that “a caddie may enter the locker room during the week to assist the player with retrieving items from his locker. Caddies are not allowed in the locker room at any other time. Players whose caddies enter locker rooms initially (not for reason provided above) will be fined $100. Subsequent fines during a season will be $250 and $500, respectively.”
