Something seems fishy to me. That's a pretty big rule change, IMO. Certainly had such a rule (that you have to keep any players involved in off-season trades) been in effect in my league, the off-season would have been COMPLETELY different. We've been wheeling and dealing, and spinning off trades and draft picks like crazy -- hell, it's been worse than the Yanks-DBs-LA negotiations.
That's just part of the fun of fantasy.
The original rule (have to keep trades) seems foolish to me and should be changed, but doing so in mid-stream strikes me as suspect.
We just had our fantasy winter meeting last night. We adopted some major rule changes by consensus, but EVERY rule change was prospective (i.e., would take effect next season). We would never change a rule on the fly unless the vote was unanimous.
I am the Master. Don't question the Master. Just do what he says and be proud.