Defining "Engaged": Farming Versus Selling Guns

For several days we've known that Obama was going to announce actions on gun regulation which he could take on his authority, without relying on Congress to pass new laws.  I've been curious to see what they would be.  Remember that his actions on immigration are currently tied up in court because, it is claimed, he needed to follow the rule-making process in the Administrative Procedure Act (APA) and didn't   So my question was: would he try the same sort of thing on guns, or could he find some other ways to affect the sale and possession of guns.

It seems that he mostly has, and partially by definition of "engaged", which I find to be a parallel with the "actively engaged in farming" issue in payment limitation regulations. (Search for "actively engaged" to see prior posts on this.)

From this Post piece (currently with 1430+ comments):

That distinction centers on the phrase "engaged in the business." Those who are engaged in the business of selling firearms, such as firearm dealers, need to conduct background checks. Those who aren't, such as individuals selling guns, don't.

 The Post piece includes an interview with a law professor, whose discussion could equally apply to the "actively engaged" issue.  To recall: as Sen. Grassley can testify, some in Congress want the USDA to interpret "actively engaged" very strictly,  others want a very loose interpretation.  Typically because the farm state legislators are more continuously involved, USDA tends to follow the loose interpretation.  This favors the farm interest: everyone actively engaged can receive payments up to the limit.  For gun control, the politics reverse themselves: everyone actively engaged in gun dealing faces the regulations on sales.

The open question at the moment is a comparison of how Obama is promulgating his interpretation of "engaged" (i.e., proposed rule under APA or simply instructions to the bureaucrats) versus FSA's use of the regulatory procedure.  More to follow.