This would seem to be true (ASA) from the way the rule is written (ASA 1 - OBSTRUCTION B-1) <font color=blue>Obstruction is the act of a fielder who is not in possession of the ball...</font>

Are there any cases where a fielder can have the ball and still be guilty of obstruction against a runner? (Leaving out obstruction of the batter).

I'm not aware of any instance when a fielder who has the ball can obstruct. Though, I do seem to remember some clinic discussion about either F1 or F3 making a feet first sliding grab of a bunt near the 1B line and tripping the B-R after gloving the ball. I'd have to think that could be either an obstruction or unsportsmanlike call - depending on what it looked like.

By rule and definition, none of the conditions for obstruction have been met. USC is another story and that would take us back to 10.1 to determine where to place the runner(s).