I reset my game recently, and quickly added codes. However I found that I was only getting 1xp on my kills because my pack was so large, regardless if I only attacked a group of one, with only one of mine equipped (I was trying different ways to get that extra xp) So I wanted to see if I could remove a member of my pack and add them back. (Hoping I could remove them all, and just attack groups of one to level faster) I tested it, and found that when I added him back, I got a message saying that I was rejected by him.
A while back I was also careless on the slayers list, and for a while attacked my own kind if they had high bounties. When adding codes, I saw quite a few "Rejected" coming back to me. I'm guessing if they remove you, or you remove them, you two can never make up and be buddies again