There is a reasonable solution.
List of permitted sources, with caveats, before the game ever starts.
"I'm sorry, I checked that feat a while back, it's on the list I handed out early as being a little too liable to be game-breaking; most the rest of the book is fine, though"
or
"I'm sorry, that book had a bit too much cheese potential for my liking; it's not on the approved book list that I already handed out."
or
"I'm sorry, I don't have that book, and haven't had time to properly check that book for balance, nor can I properly adjucate it without being very familiar with it, so it's not on the approved list that I handed out; leave it here for a week, I'll research it, and get back to you on whether or not I'll permit it, all right?"
The big thing is having the safe list (books) and the exceptions list (individual feats, spells, chapters, PrC's, base classes, combos, et cetera that lead to broken things in the otherwise safe books) distributed in advance. Then, it isn't the DM being arbitrary; the player was warned in advance.