It is the first major lawsuit in the public domain to be filed over the Swiss decision to wipe out around $18 billion of Credit Suisse's Additional Tier 1 (AT1) debt during the 3 billion Swiss franc all-share rescue deal last month, which stunned markets and alerted litigators. The appeal against FINMA, the Swiss Financial Market Supervisory Authority that ordered the writedown, was filed on April 18 in the Federal Administrative Court in St Gallen, north east Switzerland. "FINMA's decision undermines international confidence in the legal certainty and reliability of the Swiss financial center," said Thomas Werlen, Quinn Emanuel's Swiss managing partner. FINMA declined to comment and Credit Suisse did not immediately respond to a Reuters request for comment. ($1 = 0.8941 Swiss francs)Reporting by Jahnavi Nidumolu in Bengaluru; Editing by Savio D'SouzaOur Standards: The Thomson Reuters Trust Principles.

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