Who do you think manages the restricted list of account holders? If an account is restricted, and one tries to trade at a different firm, who do you think manages the database? Yes, the Federal Reserve Bank. Try and violate at Etrade, then try open at TDA, how do you think TDA knows about your violation at Etrade? It is legal compliance, firms are required to report violations to the FED. Failing to do so results in fines for the firm.
The Federal Reserve Bank.
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