by AndyDufresne on Sun Jan 24, 2010 8:53 pm
It is just the way the Foe List is coded. Right now, it essentially allows users to choose if they want to play with someone on their Foe List, but prevents those on said Foe List from joining their games.
There has been a suggestion in the past to prevent/prompt or notify a user if they are attempting to join a game with someone on their Foe List. This suggestion can be found in the Suggestions forum, most easily perhaps by a forum search.
--Andy