If you and maybe one other company sold 99% of the world's toilet paper and a major percentage of customers were forced to buy toilet paper only from you, then yes, regulating toilet paper packaging would be potentially legitimate.
Or perhaps a more real-world example would be a law that says toilet paper should not contain certain substances - like uranium, elemental mercury, crystal meth....
Or maybe a law that says your burger must be cooked enough to kill foodborne pathogens. Or maybe a law that says your raw ground beef must be stored in a specific type of box that keeps its temperature below a certain threshold...
Or that says your chicken wings must be handled and stored a certain way....