Here is the relevant text of the statute:
29180 (a) (1) Prior to making or assembling a firearm, a person making or assembling the firearm shall apply to the Department of Justice for a unique serial number or other mark of identification pursuant to Section 29181.
(2) Within one day of making or assembling a firearm in accordance with paragraph (1), the unique serial number or other mark of identification provided by the department shall be engraved or permanently affixed to the firearm in accordance with regulations prescribed by the department pursuant to Section 29181 and in a manner that meets or exceeds the requirements imposed on licensed importers and licensed manufacturers of firearms pursuant to subsection (i) of Section 923 of Title 18 of the United States Code and regulations issued pursuant thereto.
(3) After the serial number provided by the department is engraved or otherwise permanently affixed to the firearm, the person shall notify the department of that fact in a manner and within a time period specified by the department, and with sufficient information to identify the owner of the firearm and the unique serial number or mark of identification provided by the department.California's law would probably apply to 3-D printed firearms. Currently, users can print out individual components on a 3-D printer, and then assemble these components into a working firearm. This process would probably qualify as "making or assembling" a firearm under 29180(a). While I do not think that the technology currently exists for a ready-to-use firearm to be printed all at once, there would probably be a strong argument that this process would qualify as "making" a firearm. Admittedly, the statute does not define "making" or "assembling," but I would be very surprised if these terms did not apply to the 3-D printing process -- at least in its current form.
Blackman precedes his discussion of the law by noting that 3-D printing of firearms is an "overblown" concern. He remarks that it is easy to make firearms out of comment, household items without investing in expensive 3-D printing devices. Commenters on this blog have pointed this out to me before -- although I have been hesitant to do any of my own independent research making firearms from household materials for fear of ending up on some sort of watch list.
While 3-D printed firearms may not be very practical (or economical) at the moment, I think that their development is something that the law should contemplate. 3-D printing technology is developing very quickly. Usable firearms have been printed from the polymers used in typical printers, and working, metal firearms have been printed from those printers that are able to print metal components. As the technology continues to develop, it will likely become much cheaper, and if 3-D printing becomes commonplace -- the potential that somebody will use the technology to print firearms will be a very real possibility.
Blackman points out that the statute, as drafted, has some flaws. He notes, for instance, that failing to defined "assemble" means that this law may apply to people who have take apart and re-assemble their own firearms. I agree that the statute's present drafting creates the potential for some confusion. It will be interesting to see if this version of the statute makes it into law.
As I have previously noted, I think that the law will need to address 3-D printed firearms. The speed with which printing technology is developing indicates that this time will come sooner rather than later. Laws that are specific to 3-D printing technology may be the most effective way to regulate these types of firearms. Relying on laws like California's proposed statute would create a strong risk for constitutional challenges, as overly broad language in these laws may end up violating the Second Amendment.
The constitutionality of restricting 3-D printed firearms is another interesting issue, but one that will require a separate post (or posts) to fully explore. In the meantime, Blackman notes this Comment by Peter Jensen-Haxel that explores this topic. I have a few more reservations about Jensen-Haxel's treatment of the constitutional issues than Blackman, and I will plan on exploring this issue further in the very near future.