NBC News reports here on plans by states to block what they call “instructions online for making plastic guns from 3-D printers.” A more precise technical term would be CAD files. Extremetech opines here on challenges stemming from 3-D printed weapons.
Keep in mind that your typical home 3-D printer uses a feedstock of plastic that melts at very low temperatures. Such plastic is highly unlikely to produce a gun that would fire even once. Printers that can make guns that fire at all would be more expensive.
Also keep in mind that preventing one person from distributing CAD files for weapons doesn’t prevent this information from circulating. Reverse engineering products to create CAD files is common practice and reverse engineering services are widely available.
If we look at CAD file distribution as intellectual property theft, we should remember that many other products are vulnerable to this approach. It is only a matter of time, for example, before someone scans an entire automobile and posts the CAD files.