The Supreme Court invalidated the Trump-era ban on bump stoc

This is actually pretty frightening. This is a Supreme Court justice, and she actually believes that the law says something that the law doesn't say. And the majority opinion explains that in detail, with diagrams to explain it in technical detail. That she (and her two compatriots who signed onto her dissent) can claim that the decision is "inconsistent with the ordinary meaning of the statutory text" is incomprehensible. 
She then doubles down:  There is NOTHING in the federal law that mentions either "pulling" the trigger, or maintaining forward pressure on the gun. Her reasoning (if you can call it that} is a classic example of trying to legislate from the bench. It extrapolates on what the clear and plain language of the law actually is and says, and attempts to manipulate it into saying something more than what it says. 
Bottom line: since the law defines "machine gun" as a firearm that fires more than one round with a single function of the trigger, any part that converts a firearm to a machine gun must -- by definition -- be a part that changes the firearm so it fires more than one round with a single function of the trigger. Bump stocks don't do that. Bump stocks just facilitate rapidly repeating the function of the trigger to fire multiple single shots in rapid succession.