This dispute seems quite a lot like the attempt to prosecute Phillip Zimmerman over PGP in that, first, the cat is well out of the bag (and in this case has been for years), and second, as is much clearer now than in the early 1990s, government attempts to suppress publication on the Internet violate the first amendment just as they would if publication is in a book or magazine.
Moreover, the defendants' claim that the states lack standing seems right, in that the law in question, and their substantive arguments, relate to conduct of foreign affairs, which belongs to the federal government. The probability that the states could have gotten an injunction, whether permanent, temporary, or preliminary, to suppress US distribution of the code in book form is vanishingly small and likely would remain so even if sold with a CD containing the code.
In any case, these 3D printed guns appear to be expensive but inferior substitutes for old fashioned zip guns, for which google returns "about 22,800,000 results (0.50 seconds)" when queried for plans. That, and the fact that making a gun with one's own equipment is both legal and widely possible in the US reveals the controversy to be a combination of political theater and harassment. A sensible judge might reasonably have held back from puffing it up.