Michael Zeldin, a CNN legal analyst, has served as a federal prosecutor in the Criminal Division of the Justice Department and was a special counsel to then-Assistant Attorney General Robert Mueller. The opinions expressed in this commentary are his own.

(CNN) Recent criticism of the appointment of Special Counsel Robert S. Mueller by Alan Dershowitz and Ken Starr , among others, appears to have created some confusion about the reasons for Mueller's appointment and what specifically is within his investigative mandate.

As the investigation seems to be moving forward at a fast pace and in several directions, it may be helpful to take a step back and recall why Deputy Attorney General Rod Rosenstein appointed Mueller in the first place, what Mueller is charged with doing, and why it is in the public interest for his investigation to proceed to its conclusion.

The reasons for appointing a special counsel

Professor Dershowitz agrees that a "broad and open investigation of Russian involvement in our elections" should be conducted. He believes, however, that a special counsel should never have been appointed because "there was no evidence of any crime committed by the Trump administration." Starr, on the other hand, believes that while Mueller is handling the probe in a professional manner and that his investigation is not a witch hunt, its focus should only be on what happened during the 2016 election in terms of collusion, as that is the "key idea."

These perspectives reflect a misunderstanding of the legal rationale underlying the special counsel regulations generally, and/or disregard the full scope of Mueller's investigative mandate.

The Code of Federal Regulations, 28 C.F.R. Section 600.1, establishes the grounds for appointing a special counsel. It provides:

The attorney general -- or, in cases in which the attorney general is recused, the acting attorney general -- will appoint a special counsel when he or she determines that criminal investigation of a person or matter is warranted, and

(a) That investigation or prosecution of that person or matter by a United States Attorney's Office or litigating division of the Department of Justice would present a conflict of interest for the Department or other extraordinary circumstances; and

(b) That under the circumstances, it would be in the public interest to appoint an outside special counsel to assume responsibility for the matter.

Rosenstein appointed Mueller given the unique circumstances presented by this case -- the events surrounding and including the presidential removal of National Security Advisor Michael Flynn on February 13, 2017, and the activity leading up to and including the firing of FBI Director James B. Comey on May 9, 2017, in the midst of an FBI counterintelligence investigation into the 2016 presidential election.

Rosenstein determined that to "ensure a full and thorough investigation of the Russian efforts to interfere with the 2016 presidential election," the public interest required him to place the investigation under the authority of a person who would be able to exercise a degree of independence from the normal Department of Justice chain of command.

Mueller's mandate

In his order appointing Mueller on May 17, 2017, Rosenstein authorized the special counsel to conduct the investigation into the Russian government's efforts to interfere in the 2016 presidential election confirmed by then-FBI Director Comey in testimony before the House Permanent Select Committee on Intelligence on March 20, 2017 and related matters.

On March 20, Comey testified that, "I have been authorized by the Department of Justice to confirm that the FBI, as part of our counterintelligence mission, is investigating the Russian government's efforts to interfere in the 2016 presidential election, and that includes investigating the nature of any links between individuals associated with the Trump campaign and the Russian government and whether there was any coordination between the campaign and Russia's efforts. As with any counterintelligence investigation, this will also include an assessment of whether any crimes were committed."

Included within Mueller's overarching counterintelligence mandate is the investigation of:

any links and/or coordination between the Russian government and individuals associated with the campaign of President Donald Trump; and any matters that arose or may arise directly from the investigation; and any other matters within the scope of 28 C.F.R. § 600.4(a), i.e., any federal crimes committed in the course of, and with intent to interfere with, the special counsel's investigation, such as perjury, obstruction of justice, destruction of evidence, and intimidation of witnesses.

The mandate also provides the special counsel with the authority to prosecute federal crimes arising from the investigation of these matters, if he believes it is necessary and appropriate.

At the conclusion of his work, the special counsel is required to provide the attorney general with a report explaining the prosecution or declination decisions he reached, according to 28 C.F.R. 600.8.

Thus, Mueller was appointed to carry on a pre-existing counterintelligence investigation that included, among other things, determining whether there was interference by the Russian government in the 2016 presidential election and, if so, whether there was any coordination with the Trump campaign.

Contrary to Dershowitz's view, the regulations governing the appointment of a special counsel do not require the Trump administration to have committed a crime. Indeed, much of what Mueller has been authorized to investigate predates Trump's inauguration.

How Mueller appears to be carrying out his mandate

1. Potential Russian interference in the 2016 presidential election

The counterintelligence investigation aspect of Mueller's work to date that is publicly known principally involves an investigation into the actions of parties outside of the United States, e.g. the Russian government or persons who may be associated with the Russian government, to interfere in the 2016 presidential election.

One aspect of this interference was outlined in the multi-count indictment returned by Mueller this past February. The indictment charged 13 Russians and 3 Russian corporations with a conspiracy to defraud the United States through the use of social media platforms (Facebook, Instagram, etc.) to influence voter opinion against presidential candidate Hillary Clinton and in favor of candidate Trump. The second aspect, which is still under investigation, is believed to involve the hacking of the Democratic National Committee's computers and of Clinton campaign chairman John Podesta's emails.

2. Potential cooperation/association with the Russian government

Secondary to this primary counterintelligence objective is the question of whether anyone associated with the Trump campaign cooperated -- knowingly or unknowingly -- with the Russian government or persons associated with the Russian government.

Again, while no one has been charged with any criminal conduct, interest has focused on whether the Trump campaign's data analytics operation and the data research firm Cambridge Analytica potentially coordinated with a Russian social media campaign or others to influence the presidential election.

Similarly, were Mueller able to determine who hacked the DNC's and/or John Podesta's computers, he then would look to see if any individuals associated with the Trump campaign potentially conspired to receive, use and/or distribute the hacked information.

And, while former Trump national security adviser Michael Flynn and former Trump campaign foreign policy adviser George Papadopoulos each pleaded guilty to one count of making false statements, the underlying conduct that gave rise to their broader cooperation agreements may address cooperation/conspiracy with foreign nationals.

3. Matters potentially arising out of the investigation

Beyond the counterintelligence and coordination aspects of the investigation, Mueller is authorized to investigate any other matters that arose, or may arise directly, from the investigation. These matters are referred to as the "arises out" of aspect of his mandate.

The indictments of Paul Manafort, Trump campaign chairman, and Rick Gates, deputy campaign adviser, for money laundering, tax evasion and foreign registration act violations, as well as the plea agreements by former Skadden attorney Alex van der Zwaan (one count of making false statements) and California businessman Richard Pinedo (one count of identity fraud), would appear to fall within this column.

The grand jury subpoena reported to have been served by Mueller on the Trump organization also may relate to an investigation of matters not directly tethered to the counterintelligence/coordination investigation, but which may fit within the "arises out" aspect of the Mueller mandate.

4. Potential obstruction/interference in the investigation

Finally, Mueller is empowered to investigate whether, during the investigation, anyone endeavored to interfere with or obstruct his investigation. This potentially could include any conduct to interfere with or obstruct the FBI's investigation following former FBI Director Comey's March 2017 testimony.

The investigation of obstruction/interference is not straightforward, especially when it comes to the actions of President Trump. The publicly available information appears to focus on events, such as the firings of Comey and Flynn, Donald Trump Jr.'s potentially misleading statements describing the June 9, 2016 Trump Tower meeting with certain Russians, and any possible efforts by the Trump administration to have the intelligence community push back against the FBI investigation.

Conclusion

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The 2016 presidential election was unprecedented. The allegation that the Trump victory may have been achieved, in part, with the possible help of foreign nationals working in a coordinated way with Trump campaign officials is very serious.

Understanding what, if anything, occurred is of paramount importance to the nation. For this reason, the appointment of a special counsel with a broad mandate was warranted. In the interests of justice and the public interest, Mueller should be allowed to complete his work without executive or legislative branch interference.

Only when his final report is released will we know all the facts: who, if anyone, participated; what their level of responsibility was; and, most importantly, how we can prevent interference in our elections in the future.