Not even close.
Two players among the top at their positions. Can't argue with that.
I avoided CC like the plague in all of my leagues this year due to the huge amount of innings he threw last year, and him moving to the Yankees, who never seem to do well with FA pitchers, and I like Sizemore. But I still don't think that this is anywhere near vetoable.
Your post presented no evidence that there is collusion going on. There should be a sticky in this forum explaining that most posters here will tell you that collusion is about the only reason a trade should be vetoed.
The trade, while a dumb one in my book, is very allowable.
The second to last paragraph of this article is fantastic: http://www.crookedpitch.com/691/trade-them-if-you-can/