I had the same issue this season between a nephew and uncle in the league I commish, so I can understand the akward position you may feel you are in.
If the trade involves marginal value players, it doesn't make much difference. If there were a "heavy hitter" included in the swap, some other owner would almost surely object, and rightfully so.
The trade I mentioned above was a bye week fix for both teams, and I didn't make a fuss since: a) I didn't have a specific rule in place to address it, and b) no other owner questioned it.
I do feel there is an element of underhandedness in this type of transaction, and I intend to address it in '05.
"Life's battles don't always go to the stronger or faster man. But sooner or later, the man who wins is the man who thinks he can." - Vince Lombardi