And then won't release it without a court order.
However it is typically pretty easy to get a court order, because they won't fight against you in court. They just want a court to tell them to release the money, because then any money laundering isn't their fault - they're just doing what the court asked.
I’ve seen it happen, with bank accounts, and sizeable sums of legitimately obtained money. HSBC sat on several million dollars of a friend’s business for two years - they couldn’t make payroll etc., and resultantly folded. They ultimately got their money back, but it took a fortune in lawyers, court visits, etc.