As part of the deal, Fraizer Campbell moved to White Hart Lane on loan and Tottenham will not pursue a complaint against United for making an illegal approach to the Bulgarian striker.
"It's difficult to assess because there was no complaint," Wenger observed.
"We faced that problem once and we took it all the way to the end - we complained and we kept it going until the story was judged.
"It looks to me that these complaints are used as a trick for negotiations and to get better prices rather than because there is a genuine complaint.
"Berbatov went to Manchester United but Tottenham ended up not complaining so for me it has to be legal."