Reish Lakish once put a Ganav in Cherem, who in turn put Reish Lakish in Cherem. Reish Lakish was told that since his Cherem was Shelo Kedin — since a Ganav doesn’t get Cherem — his Cherem is not valid and the one against him stands. This is because for putting someone in Cherem Shelo Kedin you can deserve a Cherem.
So,
What is the text of the more Halachicaly valid Cherem by the Talmidei Hamagid?
Does it still apply?
To whom did it apply?
Does it apply to learning the Sefarim of those whom it referred to?