When did they first start making all these rules like this?
about 40 years ago
http://en.wikipedia.org/wiki/Syndex
Basically syndicated shows if someone buys the rights to that program and an "imported" station has it too, the imported station has to black it out if the main station requests syndex exclusivity.
When I lived in Duluth, MN back in 2000 we had a station from Minneapolis imported in on cable (KMSP which is now Fox)....during the day all the judge/talk/trash shows would be blacked out on KMSP9 because the local stations bought the rights to those shows. Even though they would show Springer at 3:30 in the morning on the local NBC, they were able to claim exclusivity so the 2PM version on KMSP was blacked out.
In markets where there are more than one affiliate of a network carried on cable that happens too. The local can claim it.
Why do you think on the C-Band feed there is that 2nd channel that sometimes carries programs but most of the time is color bars? Some of those programs on MeTV are carried on local stations and they request the exclusivity....so MeTV substitutes other shows at those times.
A great example is I Love Lucy....In Los Angeles KDOC has METV but I love lUcy has been on Fox 11 for 50 years and well here is what wiki says
Due to KTTV holding exclusive local rights to I Love Lucy (as they have since the 1960s; these rights are also shared with sister station KCOP), Me-TV will replace any scheduled airings of that program from the national feed with The Lucy Show instead.