Bolt action rifles over 50 are destructive devices and are regulated by the NFA. Double are exempt from this classification by the ATF. Assuming there's some logic to the law-making and a "50-cal" ban was put into effect, it wouldn't affect your double. Case in point: today a 577, 600 or 700 bolt rifle would have to be registered with the ATF as a destructive device. Under the same law, your 577 NE double does not.