A third potential reason for issuing a guidance of this sort is political: to respond to the political demand for action. Issuing a guidance document with substantial fanfare is a way to create the impression of action and satisfy relevant constituencies. To the typical, rationally ignorant voter, it may appear that the administration is doing something significant. (And insofar as Republicans complain and caterwaul about the administration’s actions, this purpose is more fully achieved.)There is this incessant need in Washington to appear to be doing something. Nothing illustrates that better than this graphic from National Journal:
Adler also reinforces that the announcement dealt with guidance, not a new regulation. This is because it takes a lot more effort to put a new regulation in place and it is possible new regulations could not be completed before the end of the administration. But guidance has no force in law, so, is the announcement meant to have a "chilling" effect (another possible reason offered by Adler) on private people selling their privately owned firearm to another private individual? A way to control activity that they have so far been unable to do by law? Is that the reason Attorney General Lynch mentioned there is court precedent for considering the sale of one firearm as being in the business?