Just blacklist him and do your best to ignore him. Informing other FC members of the situation up front would be ideal, as it could lead to some misunderstandings between this person and the FC's relationship.
We've had a couple of cases of people removed from my FC as well which then went on to try to get in through other members. It's a hassle at times, but as long as at least your most active members know about it, it shouldn't be too hard to deal with.