In the past, we've talked about how certain versions of shows couldn't be reran because the rights issues were different, due to the shows' syndicators. An example of this would be Pyramid. Sony generally owns the show, but the Cullen version couldn't be seen on, say, GSN, because CBS has the rights to it (through Viacom syndicating it). Davidson is owned by [I forget], and the $50K version Colgate-Palmolive.
However, 20th Century Fox syndicated the Clark $100K, and no one had problems rerunning that.
So my question is...what's the difference? When can whoever syndicated a show block reruns, or cause reruns to be blocked? (I mentioned CBS and Viacom above. Lots of Goodson nighttime shows were syndicated by Viacom in the 70s and 80s, yet most still got reran)