UBS's potential plan to end Credit Suisse's investment bank preservation raises concerns.

Swiss regulator FINMA has defended its decision to instruct Credit Suisse to write down its AT1 bonds to zero, saying it was a "viability event" triggered by the loan Credit Suisse received from the Swiss National Bank last week, backed by the federal government. The regulator's decision upended the usual European hierarchy of restitution in the event of a bank failure under the post-financial crisis Basel III framework, which ordinarily places AT1 bondholders above stock investors. Bondholders are exploring legal action over the contentious writedown.