“What is most concerning to me is that Mr. Mueller, who is a part of the executive branch and is supposed to follow all of DOJ’s policies and procedures, is specifically seeking to impede the ability of the president to exercise his constitutional pardon authority,” said David Rivkin, a Justice Department official under Presidents Ronald Reagan and George W. Bush.
The part of concern is described (without naming a specific rule or policy) in the article as follows:
“These waivers are troubling because they have to do with future events we can’t predict,” University of St. Thomas law professor Mark Osler said, referring to provisions in the plea deal.
Later on in the article someone else's take is presented:
However, the Harvard professor called the prosecutors' stance in the Manafort deal aggressive but not a breach of any rules or standards.
"They’ve gone about as far as they can go without getting up to the red line," he said. "But I don’t think they’ve crossed any red line."
The first quote suggests that mister Mueller "is specifically seeking to impede the ability of the president to exercise his constitutional pardon authority", but the last quote argues the opposite.
It remains unclear to me which specific DOJ policy or procedure is not followed and why. Could anyone point to the policy or procedure the first quote refers to and explain how the deal violates that?