Did the United States Court of Appeals for the Second Circuit err in deciding that a proponent of testimony pursuant to a proffer agreement is not later protected under that proffer agreement from providing testimony pursuant to a subsequently issued identical subpoena?

QUESTION PRESENTED Did the United States Court of Appeals for the Second Circuit err in deciding that a proponent of testimony pursuant to a proffer agreement, entered into with a federal governmental agency after their issuance of a subpoena, is not later protected under that proffer agreement from providing testimony pursuant to a subsequently issued identical subpoena from the same federal agency, in the same proceeding, and seeking the same testimony as that offered pursuant to the proffer agreement?