The government may simply insist that 3D printer manufacturers install software that prevents printing of a hollow cylinder of a certain size, a firing pin, or a certain type of spring.
Now iOS users can wirelessly print emails, web pages, photos, and more to their existing printer without needing to install any software or device drivers.
To create files in the WWF format requires you to install a printer driver (available for Windows and OS X) which means that only those who can be bothered to, or who are allowed to, will install the driver.