By Dave Graham, John Revill and Kirsti Knolle ZURICH (Reuters) -Swiss authorities' 2023 decision to write off 16.5 billion Swiss francs ($20.53 billion) in Credit Suisse bonds was unlawful, a court said on Tuesday, raising fresh questions about how the bank's rescue and subsequent takeover by UBS was handled. The March 2023 decision by market regulator FINMA to wipe out Credit Suisse's Additional Tier 1 (AT1) bonds during the state-engineered takeover by its old rival UBS triggered an investor backlash a ...