The official bats used for league and tournament play in Fond du lac is the same that is used for ASA Championship Play.  Please pay special attention to the bats that are no longer grandfathered in.  A prime example would be the original Miken Freak.  This is not the Miken Freak 98, which is approved and bears the ASA 2004 certified stamp unlike the original Freak..

From the ASA Website

…Bats must meet all of the requirements of Rule 3, Section 1 and:

1. must bear either the ASA approved 2000 certification mark or the ASA 2004 certification mark as shown below, and must not be listed on an ASA non approved list, and
   
2. must be included on a list of approved bat models published by the ASA National Office; or
3. must, in the sole opinion and discretion of the umpire, have been manufactured prior to 2000 and if tested, would comply with the ASA bat performance standards then in effect.

Beginning January 1, 2004, all bats in ASA Championship Play must pass the ASA 2004 bat standard. All bats having the 2004 certification mark will be allowed in ASA Championship Play. Bats that have the 2000 certification mark will not be allowed in ASA Championship Play unless they are listed on an approved bat list on the ASA website. For convenience, the ASA website has a listing of bats that do not pass the ASA 2004 bat standard.

Click here for ASA’s 1 Page Non Approved Bats with Certification Marks (2000 and 2004)
(current listing, no changes as of January 5, 2011)

Click here for ASA’s Non Approved Bats with Certification Marks (2000 and 2004)
(current listing, no changes as of January 5, 2011)

Click here for ASA’s Non Approved Bats with 2004 Certification Marks
(current listing, no changes as of January 5, 2011)

Grandfathered Bats No Longer Authorized Beginning in 2008

ENTIRE LIST OF CERTIFIED BATS

Please consult the lists above if you are going to purchase a new bat.

I also recommend to managers that they print off a list of banned bats and keep it in your bat bags for reference.