is there anything i can do about fantasy league commissioners cheating?

Yahoo! probably doesn't monitor the leagues - too much going on in too many leagues. But they do probably respond to complaints and it sounds like what you're talking about is very much something to complain about. Might help if you can get other members of the league to complain as well.

It looks like commissioners have the power to change rosters as well (first link below), so I wouldn't be surprised if there was some way for a commissioner to do what you're talking about.

The second link addresses your question I think and they recommend sending in a complaint (there's a button at the bottom of the page from the second link that says to contact customer care). I'd assume you should include the league name and number, and describe the situation and the specific teams.

Report him to yahoo terms of services. Maybe they can help you. Don't understand how he got the good players off of waivers. Didn't anyone else try to pick them up?

If it is a custom league then probably very little as he can set the rules and regulations.

I dont know but that is f'n weak dude