Baseball rules question

Yesterday, I found myself with a ticket to a baseball game with front row seats on the field level, just on the fair side of the foul-pole. In other words, home run territory. Sitting in the seat, I started daydreaming about the chances of catching a home run ball, but I also realized that unless the ball was a line drive homer, the left fielder would have plenty of time to saunter over and take the ball out of my hands since it was in the first row.

So then I got to thinking: say the batter hits an absolutely towering shot that gives the fielder forever and a day to get into position to make a play, but the ball is clearly going to land in the stands somewhere. We see highlight plays fairly often where a player runs up the outfield wall or dives into the stands to try to make a great catch.

But what if the player had time to actually climb the wall and into the stands to get into position? Is this legal? Can a player actually leave the field of play in order to make a catch? And is there a distinction between balls hit into fair or foul territory in such a circumstance?

Just curious.

I believe that being in the stands would count as being “out of play” and any catch made out of play would not count. But I’m not a baseball rules guru, just a former softball umpire.

So basically, if a fielder is completely off of the field of play at the time of the catch, it does not count.

The rules state:

Which implies that he can’t fully leave play and set up for the ball.

From the definition of “Catch”:

(http://mlb.mlb.com/mlb/official_info/official_rules/definition_terms_2.jsp)

There’s also this:

But that appears to only apply to foul balls.

That’s all I could find. I thought perhaps there would be a specific prohibition on fielders “leaving the field of play” while the ball is live or somesuch, but nothing. They have to be positioned in fair territory when the ball is put in play, but obviously they can leave fair territory to make a catch.

An aside: I find it interesting that the home team’s manager makes the determination whether the field is fit for play or whether the game should start because of weather. I always thought that was the ump’s call.