This sounds more like an OSHA thing than a union thing. I don't know anything about OSHA regulations with respect to big trucks except that they exist, but since they exist I'm willing to bet "shouldn't be driven by drivers without a CDL" is in them. Edit: asked around and it may actually be FMCSA that would object, but they are "notoriously slow about responding to complaints."...and wouldn't it be lovely if this show turned and the Teamsters came in and said "no, you're not allowed to drive an airbraked 10-ton truck at all without a commercial endorsement, let alone up a winding mountain road of dirt in the pouring rain
From a very lay perspective. OSHA is more about like, pathogens and shit (health concerns, basically, lots to do with regulating chemicals/solutions and exposure) but could potentially also address things like sleep/time allowed to work nonstop (like truck drivers). CDL license is definitely gonna be a Department of Motor Vehicles/cop thing - if the driver of a truck were pulled over and didn't have a license I assume both he and his employer would be in deep shit for essentially driving w/o license, etc. As for the safety of the truck or how the truck is being used (safe vs. unsafe conditions), not sure about that. Could maybe be OSHA, but feel like there should be some other set of regulations that covers it. Course, out in the middle of bumblefuck with no cops around to catch road safety violations, probably pretty easy to violate without consequences.