Sen. Rand Paul (R-Ky.) (YouTube)

(CNSNews.com) -- When asked whether the appointment of Robert Mueller as special counsel to investigate alleged Russia-Trump campaign collusion is unonstitutional, Sen. Rand Paul (R-Ky.) said he was "not an expert" on this "particular" constitutional issue but believes there is a “strong argument” that the Senate should have approved Mueller's appointment.

Sen. Paul added that he believes “Mueller should not have been appointed.”

At the U.S. Capitol on Tuesday, CNSNews.com asked Sen. Paul, “Professor Steven Calabresi of Northwestern Law School and Mark Levin have argued that Robert Mueller’s appointment violates the Appointments Clause because he is a principal officer exercising at least the authority of a U.S. attorney but was not confirmed -- appointed by the president or confirmed by the Senate. Do you agree that Mueller’s appointment is unconstitutional?”

Senator Paul said, “I think they make a strong argument that someone granted this much power is of the level that should be approved by the Senate. So I think that Mueller should not have been appointed. And I think really we should set an example by not doing this again.”

“Okay, so you, would you agree that it’s unconstitutional?” asked CNSNews.com.

“I’m afraid I’m probably not an expert in the exact whether this particular issue is constitutional or not,” said Paul. “But I think there is a strong argument to be made that when you appoint somebody who’s at this level that it should be something that’s approved by the Senate.”

Special Counsel Robert Mueller, who was appointed to his position by Deputy Attorney General Rod Rosenstein. Mueller was the FBI director under President George W. Bush and in the first term of President Barack Obama. Obama appointed James Comey to replace Mueller as FBI director in 2013. Comey was fired by President Trump in May 2017.

Professor Steven Calabresi has made the argument that Mueller’s appointment is unconstitutional under the Appointments Clause of the Constitution because Mueller was not appointed by the president or confirmed by the Senate, and yet has been given the same power as a “principal officer.”