On February 1, 2011, FINRA Rule 4160, Verification of Assets, was put into effect. This rule states that if the following conditions are true:
1. A member keeps assets or records at a non-member institution,
2. FINRA has asked the non-member institution to verify what assets or records are being kept for the member, and
3. The non-member fails to promptly provide verification,
Then FINRA will notify the member that they are prohibited from keeping assets and records with the non-member.
http://www.finra.org/Industry/Regulation/Notices/2010/P122526