Pretty simple, really... It's in the rules:
QUOTE
IR RULE:
You can not activate a player in the same week you put him on IR.
You can not put a player on IR in the same week you acquired him.
If you don't activate a player on IR the week after he has stats you lose him.
A player qualifies for IR by being listed as OUT or DOUBTFUL on the official NFL injury report.
Suspended players are not allowed to go on the IR. They are not on their team's IR so they shouldn't be on yours.
Technically, Bell could have stayed on IR up until kickoff next week. At that point, I would have had to drop or activate him. I activated him tonight, however, just because I don't feel it's worth causing a "stir" over. All of that said, I would be more than happy to put this rule up for a vote (for next year), if multiple owners feel it needs to be changed.
Edit: Seriously, if others have a problem with this rule, let me know, and we'll vote on it for next year. If not, and I don't hear anything, I'll assume it's fine as is. Thanks.