An organization called the Arms Keepers wrote a brief in the McDonald case. In it, they argue for an odd model of “selective” incorporation through the Privileges and Immunities (PorI) clause, while strangely insisting that Slaughterhouse can (and possibly should) be preserved.
They were just formed this year, and there’s scant information on them. Their website is registered to a lawyer named Andrew Hyman. The brief describes them as, “a volunteer organization that supports reasonable regulation of handguns and rifles, instead of prohibition.”
The phrase “reasonable regulation” is a red flag, being appropriated as it’s been by the Brady Campaign, and it makes me wonder.
Alan Gura has a few notes on the matter. Apparently, Orin Kerr is involved with Arms Keepers and was one of the co-authors of the brief. Although he seems open to the idea of visiting PorI, he cast some grim predictions about its revitalization on the Volokh site.