Yes a good thing. I agree that actual bump stocks are sort of silly, but the ruling says the atf can not interpret a law differently than it’s written. The whole case was about atf reinterpretation of the law and banning things that met the letter of the law. The dissent was basically the laws intent was to ban rapid fire, thus the reinterpretation is ok. Problem was the law said nothing about rate of fire. It simply says a machine gun will automatically fire more than one shot with each function of the trigger. A bump stock does not do this.
congress can easily make a law to ban bump stocks and that I believe would be legal. This ruling clarifies that the president can not have agencies make new rules/interpretations when they can’t get the law passed.