The regulations change constantly, especially with the arrival of cryptocurrency which has been a regulatory nightmare.

There are two primary reports filed by banks. CTR's and SAR's. The latter they cannot say anything about and they cannot offer regulation or anything. This is why all banks have the same notice "in an effort to aid the government... blah blah blah". However, on CTR's they CAN point out the regulations, BUT ONLY if a customer specifically asks about cash transaction regulations. Which is misleading because CTR "cash" also includes money orders, digital currency, wires, checks, etc... depending on the amount and the situation.

When a bank employee sees a red flag that may lead to a SAR, they basically have to shut their mouths. They also don't know that a SAR will be filed, they report it internally and that decision is made elsewhere. Nobody with any knowledge of even the suspicion is allowed to say anything to anyone. Not even the police, and not even federal agents. There is a specifical procedure the government contacts you if they need to discuss it and often the bank will require an ID number to be recited that they attached to the SAR before they'll even speak to them.

On the seized check, one the transaction starts it’s at the bank’s discretion because it’s an evidentiary document. Since she was causing such a fuss, they likely just made a copy of it (which is all that is technically required) which means it might have just been a stall tactic to do that, but they are allowed to take so long as there is reasonable cause, and for no other reason.

Cash has to be confiscated by law now and given to the Secret Service.