alt Hacker NewsBanks can just ban you if they whisper the magic words "suspected money laundering". They are theoretically accountable to a process that takes 500 years and 3 quadrillion dollars to reach a resolution, then they will unban you. You might notice both you and the bank will be dead by that time.
I actually know someone this happened to. While they did ban him from using the bank, they first warned him, gave him a chance to close out his open transactions, and then helped him move all the money somewhere else at no cost.
The important part is that they can't just close your account and keep everything.