Why? Because nobody is manufacturing Death Stars anymore. Besides, the Constitution doesn't say anything about "The right of the people to keep and bear the arms the New York Times approves of shall not be infringed."
Or, to put it another way, why this weapon, designed to obliterate whole planets and shoot down stars, should be banned is a question that should be put to the hoplophobes who get oogey everytime they see a BB gun and the politicians who shamelessly do their bidding.
For some odd reason, they neglect to mention that AR’s are banned in many states to hunt deer because the caliber is deemed insufficient for an ethical kill of the animal.
Yet we are to believe the Slimes when it claims these are uber powerful weapons.