There could be. I would look at the entire population of "new bank customers" vs the actual customers that would be in your "footprint". Do the excluded customers fit into any protected group? Check the census tract income levels of the excluded areas. Understand all those demographics and then give it the "smell" test. Understand the reasons why the credit card department wants to restrict the offering. Do they make sense from a Fair Lending perspective.
An example of a good reason might be, we want to confine the offering to the state of our home office, due to a lack of expertise in other states' requirements.
An example of a bad reason might be, we want to exclude the north part of the city because there are so many minority low income customers there.
If you end up with a plan to go ahead with the project, make sure the credit card department has documented the due diligence done and that risk management has been included. If the credit card department is not willing to put it in writing, then don't proceed.
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"No problem can withstand the assault of sustained thinking." ~ Voltaire
"Sustained thinking gives me a headache." ~Me