Norman Eisen is a senior fellow at the Brookings Institution and was President Barack Obama's "ethics czar" from 2009 to 2011. He is the author of " The Last Palace ." Eisen is chairman of the board at Citizens for Responsibility and Ethics in Washington (CREW), a non-profit organization, where Conor Shaw is counsel and Gabe Lezra is public advocacy counsel. The opinions expressed in this commentary are their own. View more opinion articles on CNN.

(CNN) Special counsel Robert Mueller and his investigation have been beset by smears . Now another one is afoot: the claim that Mueller's appointment as special counsel was unlawful.

With Friday's New York Times story targeting Deputy Attorney General Rod Rosenstein (in our view spun up by a source or sources to try to sow the seed of President Trump's ire) it is more important than ever to put this other canard to rest.

The latest iteration of this fabrication, advanced by Andrew McCarthy in a recent piece in the National Review, argues that Deputy Attorney General Rod Rosenstein's appointment of the special counsel was procedurally unsound because Rosenstein's order effectuating that appointment failed to specify potential crimes committed by the President that Mueller must investigate.

McCarthy and others who advance this attack are dead wrong. Indeed, though it is conveniently ignored by some, the claim has been repeatedly turned aside by the courts. No fewer than three federal judges (a Reagan appointee , an Obama appointee and a Trump appointee ) have rejected challenges by defendants claiming that Rosenstein's delegation was insufficiently specific to justify Mueller's prosecution of their case. Their reasoning, and other evidence, explains why this claim is wrong and deeply so.

Attorney general's authority

The argument fails, first, because Congress has given the attorney general broad authority to delegate the investigation and prosecution of matters to whomever he or she sees fit.

By statute, the attorney general may "from time to time make such provisions as he considers appropriate authorizing the performance by any other officer, employee, or agency of the Department of Justice of any function of the Attorney General."

Congress has further authorized the attorney general to commission special attorneys who may , "when specifically directed by the Attorney General, conduct any kind of legal proceeding, civil or criminal, including grand jury proceedings and proceedings before committing magistrate judges, which United States attorneys are authorized by law to conduct..." As Rosenstein explained in a June 2018 letter to Sen. Chuck Grassley, (R) IA, neither these provisions nor any other requires the attorney general to "identify criminal violations before appointing a Special Counsel from outside the Department."

The Department of Justice's internal policies for the appointment and management of special counsel also create no obligation on the attorney general to publicly announce what particular crimes or individuals a special counsel is investigating.

The policy merely states that a special counsel will be appointed when three conditions are met: 1) the attorney general "determines that a criminal investigation of a person or matter is warranted;" 2) either the "investigation or prosecution of that person or matter ... would present a conflict of interest for the Department" or there are other extraordinary circumstances; and 3) the appointment of an outside special counsel is in the public interest.

Each of these three preconditions were met in the current special counsel investigation. By the time of Mueller's appointment, criminal investigations of former Trump campaign chairman Paul Manafort, former Trump campaign adviser and White House National Security Adviser Michael Flynn, and of Russian hackers were apparently underway; the President's firing of FBI Director Comey on May 10, 2017, also justified investigation of a separate subject: obstruction of justice by President Trump (who maintains he did nothing wrong and calls Mueller's probe a "witch hunt").

Firing of Comey

Indeed, President Trump's firing of Comey -- for disloyalty or for his handling of the "Russia thing" -- was what created the extraordinary circumstance that satisfied the second prong of the policy.

If that standard is not met in the case of a president firing the head of an investigation into the president's campaign, it is not clear when it would be. Finally, the interest in ensuring that the ongoing investigations were insulated from further political influence was sufficient to satisfy the final prong. There is no requirement that these determinations be made or justified in a public document.

Another provision of the policy requires that the special counsel be "provided with a specific factual statement of the matter to be investigated." Essentially, this requires a simple recitation of the facts that constitute the matter that needs to be examined.

Rosenstein's May 17, 2017, order authorizing Mueller "to conduct the investigation confirmed by then-FBI Director James B. Corney in testimony before the House Permanent Select Committee on Intelligence on March 20, 2017" satisfies that requirement. The order further clarifies that that investigation included "(i) any links and/or coordination between the Russian government and individuals associated with the campaign of President Donald Trump; and (ii) any matters that arose or may arise directly from the investigation; and (iii) any other matters within the scope of 28 C.F.R. § 600.4(a)."

In an August 2, 2017, memo to Special Counsel Mueller (most of which has yet to be publicly released), Rosenstein provided the special counsel with an even more specific delineation of his jurisdiction. Mueller has respected those limits: Matters beyond his designated jurisdiction -- including the investigation of the President's personal attorney Michael Cohen and potential cases against individuals with no direct connection to the Trump campaign -- have been referred to other components of the Department of Justice.

So, while Cohen may be providing Mueller with information r egarding the questions of Russian collusion, Cohen was charged and sentenced by a separate entity within the Department of Justice for his crimes that were unrelated to Mueller's investigation.

Attempts to discredit special counsel are off base

Past practice provides even more evidence that these attempts to discredit the special counsel are off base. The 1999 appointment of Special Counsel John Danforth to investigate the government actions during the 1993 siege of the Branch Davidian compound in Waco, Texas, did not specify crimes for investigation or identify any individuals as subjects. Indeed, at the news conference announcing his appointment and laying out his authority, Special Counsel Danforth could not say whether his investigation would be a "criminal review" or an "administrative review."

Even if there were some technical deficiency in the form of Rosenstein's order appointing Mueller, each of the three courts upholding special counsel Mueller's appointment have further noted that DOJ policy explicitly does not create any enforceable rights. That is, the DOJ regulations explicitly explain that potential litigants cannot use the regulations as grounds for a lawsuit.

Finally, on the merits, there is no credible argument that the American people are improperly being kept in the dark about what Mueller is investigating. Prior to taking public action in a case, there are good reasons for a prosecutor not to inform the subjects of investigation precisely what statutes or theories are being considered. Indeed, it is DOJ policy to comment on an investigation only when it is necessary to assist the criminal investigation or to protect public safety in part because there is a risk that doing so could unfairly damage the reputation of an individual who may never be prosecuted.

Follow CNN Opinion Join us on Twitter and Facebook

When the special counsel has spoken, it has been through action. Mueller's answer to the question "what is the crime?" is "many," and his team has chronicled them in indictment after indictment, guilty plea after guilty plea. Those successes should not be demeaned by smears like this one.