Tom,
I'm in Houston today and just shot a IDPA sanctioned match with the PSC club. Everybody here had concealment even though I'm sure not all are CCW permit holders - I know because I overheard a CCW instructor telling a number of the shooters (who happened to be all women) about the CCW class.

Haven't we been shooting from concealment in IDPA long before CO passed the "shall issue"?

I checked the final rule book from February 2005 and it specifically exempts concealment when wearing "duty gear" but otherwise concealment is required "where appropriate". In the previous version of the rule book not drawing from concealment was a procedural error, but the current rule book doesn't mention that. Nor does the current rule book define "where appropriate" but I would guess that means stages where the gun is other than in the holster, like some of the recent scenarios.

Are you sure about the state prohibition in sanctioned matches about concealment when not a CCW holder?