Sweet catch. Milwaukee is an all-around good club. If Shaw ever gets his hand/wrist thing fixed their lineup is nasty. I still hate them, just for Selig purposes.
Once the ball goes into the stands it's fair game. eta: you would hope the idiots don't mess with an Astros fielder, and mess with all of the opponents. Legally, of course.
Once the ball is out of play and into the stands, you can do almost anything to prevent a catch. Almost, within reason. You can't touch the player, you can't grab their glove or anything, but you can sure knock it out of the way while you're going for the ball