In my experience, it’s legal because that’s what federal banking regulations instruct the bank to do. Banks don’t make these decisions arbitrarily. There are investigations and in some cases it involves federal agencies that investigate financial matters. The Bank Secrecy Act literally prevents banks from discussing the matter with you.
Part of the issue may involve where some of the funds came from. If any of the funds were transferred to you, by someone that obtained the funds in a questionable way, it involves you financially in the activities. I’m being deliberately vague, because the details you’ve presented are vague, but accurate for the limited information I have. I’m happy to provide the terms and conditions and contact information for Apple and Green Dot Bank. Apple will have less information than Green Dot, because they are not involved at all. Green Dot is prevent from disclosing information to you, as well as Apple.
You can dispute anything you want. But in that won’t change a thing in the largest percentage of cases. But, I’m not a lawyer and I don’t give legal advice.