[Rich Ives]

Originally Posted by MrUmpire

The actual rule:

6.06 A batter is out for illegal action when-

(c) He interferes with the catcher’s fielding or throwing by stepping out of the batter’s box or making any other movement that hinders the catcher’s play at home base.

____________

Notice the lack of the word "intentional."

Keep in mind that we don't want the catcher just plunking the batter to get an interference call.

MLBUM 6.10

If the batter interferes with the catcher's throw to retire a runner by stepping out of the batter's box, interference shall be called on the batter under Official Baseball Rule 6.06(c). (See Section 6.8.)

However, if the batter is standing in the batter's box and he or his bat is struck by the catcher's throw back to the pitcher (or throw in attempting to retire a runner) and, in the umpire's judgment, there is no intent on the part of the batter to interfere with the throw, the ball is alive and in play.