A few weeks after Hillary Clinton was sworn in as secretary of state in early 2009, she was summoned to Geneva by her Swiss counterpart to discuss an urgent matter. The Internal Revenue Service was suing UBS AG to get the identities of Americans with secret accounts.

If the case proceeded, Switzerland’s largest bank would face an impossible choice: Violate Swiss secrecy laws by handing over the names, or refuse and face criminal charges in U.S. federal court.

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