Except he wasn't acting in the capacity of an attorney representing the Commonwealth. He was acting in his capacity as Director of the FRB and, according to the SJC, as an administrator he made the determination that jammed up Simkin.
From the SJC opinion: "regarding the incident on November 6, Guida determined that Simkin was no longer a"suitable person" to possess a firearm in Massachusetts. Specifically, Guida made this determination on the basis that (1) Simkin's visit to the medical office while "heavily armed" fell outside the "business activity" of buying and selling firearms that Simkin indicated on his license application as the reason he sought the license; (2) Simkin caused "fear and alarm" at the medical office; and (3) Simkin used a false name in order to conceal his identity."
As the FRB director, was he merely carrying out policy directives issued from higher up? I don't know.
But the whole just representing a client and doing your job excuse only goes so far.
Martha Coakley is just representing the Commonwealth as AG. David Linsky is just representing his constituents as State Rep.