Merkley's letter follows steep losses at Credit Suisse Group AG from holdings of distressed credit and securitized loans of distressed assets – holdings that Credit Suisse's own top executive was reportedly unaware of until the losses occurred. "Credit Suisse's apparent failures to effectively oversee its risky trading operation bring to the surface an on-going concern I have regarding whether the Volcker Rule, which former Senator Carl Levin and I helped draft, is being implemented as intended," wrote Merkley. "As its authors in 2010, we intended the Volcker Rule to be a modern Glass-Steagall Act that separates high-risk trading activities from banking organizations that serve customers by making loans and facilitating the raising of capital.