Around 10 months after the lawyer began attending board of trustees meetings, the board passed a resolution prohibiting members of the public from making audio recordings of board meetings.
In response, the lawyer attended another board meeting and placed a dictaphone on the table.
When questioned about whether it was operating, the lawyer declined to answer.
Following a second similar incident, he was served a trespass notice by the board.
The board complained to the Lawyers Complaints Service that he had breached rules 10 and 11 of the Lawyers and Conveyancers Act Rules 2008.
The standards committee said it considered the lawyer had engaged in a "sustained campaign" against the board and his letters were "unnecessarily intimidating, discourteous and inappropriate".
"It considered that [the lawyer] had taken issue with frivolous matters in a particularly strident and forceful manner, which would have been likely to lead to the incurrence of unnecessary cost to the [board], and that it reflected poorly on [the lawyer] and the profession," the committee said.