California, Colorado, Delaware, Hawaii, Illinois, Iowa, Minnesota, North Carolina, Rhode Island, Vermont, and Virginia were added in a Thursday court filing to the list of eight mainly Democratic-controlled states and the District of Columbia who sued the U.S. government in federal court.
The states behind the lawsuit argue that publishing blueprints would allow criminals easy access to weapons. Gun rights advocates say fears about 3-D printed guns are largely overblown, based on current technology.
The blueprints were originally set to go online on Wednesday, following a June settlement between the U.S. government and Texas-based Defense Distributed allowing the group to legally publish the designs.
Defense Distributed, founded by self-declared anarchist and gun rights advocate Cody Wilson in 2012, has argued the publication is protected by his First and Second Amendment rights, respectively to free speech and to bear arms.