The state of Massachusetts passed a right to repair law in 2013 that allowed anyone access to the full diagnostics systems in their car. This law was essential to ensure that everyone had access to vehicle diagnostics to correctly repair vehicles.
There is no law that protects consumers or SEMA members right to modify vehicles. So at any time safety regulations thru NHTSA or any other government agency could stop customization. SEMA has put a lot of effort into emissions regulations, but with EV and autonomous vehicles, our biggest threat is around safety systems.