Our debit card processor told us that per a new a law, Visa isn't allowed to give us copies of receipts or other documentation when we are investigating a debit card dispute. She went on to say that if we pursue trying to get the documentation without a court order we could be fined.

I don't know what "law" she is referring to.. Any clue? It sounds fishy to me.

You might want to refer them to the actual rules rather than making something up. Start with 11.1.3.2 Retrieval Request Fulfillment Requirements (Updated)

http://usa.visa.com/download/about_visa/15-April-2015-Visa-Rules-Public.pdf

thank you!