PIX 6.x does not have the Layer 2 MAC ACL feature. So, there is no straight-forward way of doing this.

The only think that may work (but it is a bit of a kludge) would be to enable aaa authentication/authorization for through traffic, and then use a mac-list to exclude everyone but the MAC you want to deny. Actually, you can just use a specific deny followed by a permit for everyone else. That would require the specific MAC to be authenticated/authorized. ...just a thought, but I'm not sure I would recommend it. It would depend on the amount of traffic the PIX was passing.

Sincerely,

David.