John Fay reports that a Reds spokesman said ballpark officials have the right to eject the fan, but they usually don't. One would assume that officials try to determine the fan's intent and whether there was malice involved.

What happens if a fan interferes in a baseball game?

Definition. In every case of spectator interference with a batted or thrown ball, the ball shall be declared dead and the baserunners can be placed where the umpire determines they would have been without the interference.

Can an umpire eject a fan?

Yes, an umpire is allowed to eject any fan who enters the playing field or a restricted team area.