Did Mark Pieth Threaten a Journalist with Legal Sanctions?

The letter from journalists to Mark Pieth (which I discuss here), chair of the FIFA "Good Governance" committee, contains an explosive allegation -- that Pieth threatened a journalist with legal action in order to try to keep hidden FIFA's payments to him:

[W]e are concerned that Professor Mark Pieth, through an employee, threatened legal action against one of our colleagues investigating how much Pieth was paid by FIFA and how much he will get from FIFA in future for the work in the so called Independent Governance Committee (IGC), although Professor Pieth eventually confirmed the figures.

I do not know Mark Pieth, though he is widely respected in the community. Thus, I find the allegation levied above to be both remarkable and troubling, especially so for an academic who has written the following (p. 188, here in PDF) in the context of recommendations on "good governance" to the United Nations:

In order to safeguard against conflict of interest situations, a robust financial disclosure and conflicts of interest regime should include a requirement that all United Nations staff and consultants, including "$1 dollar a year consultants," disclose in writing to the Ethics Office any financial interest or business relationship of his or her own or of immediate family members that could represent a conflict with his or her responsibilities or that could reflect unfavorably upon the integrity of the Organization.

Pieth should respond to the allegation.