Federal Motor Vehicle Safety Standards (FMVSS) are U.S. federal regulations specifying design, construction, performance, and durability requirements for motor vehicles and regulated Automobile safety-related components, systems, and design features.
Within those standards there is a vehicle certification process. It requires a federal certification label be attached to all vehicles manufactured under its purview. The certification label MUST display the vehicle’s GVWR, total weight a vehicle has been built to safely weigh, including passengers and cargo.
The only way the GVWR can be altered is by the vehicle manufacturer or a certified vehicle modifier.