The AMA recognizes organizations that represent some form of aeromodeling. The AMA lists as many as 24 Special Interest Groups. The AMA has forms that can be submitted to the AMA if a group wishes to receive SIG status with the AMA. I am not sure if the AMA has a definition for what a SIG really is. Furthermore, I am not sure what the purpose of a CL Forum SIG would be. And I think there would be some problems with filling out the SIG application in the name of a CL Forum.
As has been mentioned, there are SIG's for Aerobatics, Carrier, Speed and Racing. There is a SIG for Scale, the National Association of Scale Modelers which encompasses RC, FF and CL.
To clarify some statements above, the Miniature Aricraft Combat Association, MACA, for CL Combat, is alive and well.
Check out:
http://www.maca.hobby-site.com:3535/The National Free Flight Society is the SIG recognized by the AMA for all of the FF events, including indoor. In fact, I think the NFFS is probably the first so-called SIG recognized by the AMA years before there were any CL SIG's. I think the nature of the FF events allows those events to be represented by a single SIG and it seems to work well as far as the AMA and the Free Flighters are concerned.
I cannot speak for the other SIG's, CL or otherwise, but the purpose of the SIG status of PAMPA is to assist the AMA in the conduct of the Nats and the FAI CL Aerobatics Team Trials. However, the roll of PAMPA in these events might seem a bit unclear to the casual observer. The CLPA events at the Nats are run by the Nats CLPA Event Director under the direction of the Nats organizers and the Director of the Nats CL events. Announcement about the Nats stunt events are made in the PAMPA newsletter as are calls for volunteers. For the most part, the volunteers at the Nats, including judges, tabulators, pull testers, pit bosses, and on and on are for the most part, but not always PAMPA members. I think the AMA depends on the other CL Sig's for the same functions at the Nats. For the FAI Aerobatics Team Trials, these are planned and determined by the AMA FAI Control Line Aerobatics Team Selection Committee which has nothing to do with PAMPA. However, the Team Selection Finals Event Director depends heavily on volunteers, mostly from PAMPA, to make the Team Trials work.