The Forgotten Regulation: Right to Financial Privacy
Maybe forgotten isn't always the right word; perhaps "unknown" is more appropriate. I can't tell you how many banks I've been to that had no idea this regulation even exists. The good thing is that it's not very hard to set up a program to comply.
I like this regulation because it's the federal government actually limiting its own reach for a change. Here’s the gist - the basic premise is that this regulation "establishes specific procedures that federal government authorities must follow in order to obtain information from a financial institution about a customer's financial records." In other words, you as a bank need to protect your customers from federal (not state) information requests. Here is a link to the FDIC compliance examination manual for more details. It's only two pages, tells you what you need to do, and even has some aids to help you comply. Don't forget about this simple regulation. It applies to everyone!