A sensible ruling...

Via Guns.com: 

A Ohio judge last week rejected a prohibition adopted by the city of Columbus on bump fire stocks, hitting city officials with a permanent injunction against enforcing the ordinance. Judge David Cain, writing for the Franklin County Common Pleas Court, found that the city’s ban did not square against state preemption law which prevents local governments from regulating firearms.

In responding to the legal challenge, Columbus argued that since a regular firearm stock can be replaced with a bump stock, it is an aftermarket accessory and not a factory gun component, thus making it open for the city to regulate. Cain refuted that logic, saying, “it is clear that the bump-stock, when installed, becomes an integral part of the safe operation of a firearm. As such, a bump-stock is not an accessory of a firearm, but a component of a firearm.”

Cain applied the test used by Columbus in attempting to justify their local ban on bump stocks by substituting an auto parts analogy– one that used spark plugs instead of stocks.

A person can go to a local auto store and buy replacement spark plugs. In fact, a person can buy spark plugs that create more horsepower in an engine. These spark plugs can then be installed by the end-user of the car. Columbus would have to argue that spark plugs are now accessories and not components. As can be seen, this conclusion is untenable. Regardless of who installs spark plugs, they are components of an engine. Similarly, a bump-stock, regardless of who installs it, is a component of a rifle.

Read more here.