by Comp » Sun Jul 17, 2011 10:02 pm
Its rather long to type the whole rule, but its ASA 8-1-D (1-4) if you have access to a rule book.
But the main section of the rule dealing with this situation is D, "When a catcher obstructs a batter's attempt to hit a pitched ball."
Generally speaking, withdrawing the bat is just that and is not an attempt to hit the pitch. To go along with what MTR said above, in some cases the batter may show bunt, pull back and then swing, but it would ultimately be the umpires judgement as to if it were an attempt to hit the pitch or was simply withdrawing the bat.