There are safety regulations that require things roughly like, "to prevent harm to planes in the air and people on the ground, either control where your satellite re-enters so or make your satellite entirely out of components that are almost certain to burn up on re-entry".
As far as I can tell, there is no environmental regulation of how many kilograms of aluminum, silicon, etc. being added to the Earth's atmosphere when a Starlink burns up during re-entry.