Doug, I wouldn't go out and play the lottery just because I'm chiming in, but I hope your luck continues.
For those who are not aware, beginning April 19th, MasterCard will transfer liability to the acquiring bank for counterfeit ATM withdrawals that are done using a chip (EMV) card. This technology is not widely used in the United States, but it is the standard for most international banks. As tdogz correctly points out, our risks are pretty minimal until more U.S. banks begin issuing chip cards.
To answer the original question asked, since ATMs are run on PIN networks, VISA/MasterCard rules are silent on whose cards you must accept for withdrawals. You should look to your card processor's network rules to see what is and is not permissible and what signage is required. Personally, I wouldn't make a mountain out of a molehill just yet. (That isn't to say that when last week's Wall Street Journal published an article on this topic our midwestern bank CEO wasn't at my desk before the bnak opened asking what we should do.)
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Sola Gratia, Sola Fides, Sola Scriptura, Solus Christus, Soli Deo Gloria!
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