Sen. Graham, R-S.C., said on "Hannity," he believed that with Mueller deciding President Trump did not collude with Russia and not to bring an obstruction of justice case against him, the investigation is over.
"When [Mueller] met with Barr personally... weeks before the report was given out, he told Barr, I can't decide about obstruction... but I did not make my decision based on DOJ policy that you can't indict a sitting president," Graham, chairman of the Senate Judiciary Committee, claimed.
Graham said Mueller did not find proof there was, "no collusion with the Russians. He decided not to bring a case against the president based on obstruction."
"To me, case closed. Let's look at Comey and McCabe, [former FBI Agent Peter] Strzok, [former FBI lawyer Lisa] Page [and] all these other people, and see how we got into this mess to begin with," he added.
The senator noted Connecticut federal prosecutor John Durham is examining the origins of the Russia investigation.
"Durham is going to look at all of these cast of characters to see if they broke the law. And, Barr is going to make sure that the DOJ is reformed so it's never abused in this way in the future," the South Carolina lawmaker added.
Graham said he is also awaiting a report on from Justice Department Inspector General Michael E. Horowitz on potential surveillance abuses at the FBI.
"So, Horowitz will issue his report about the FISA warrant process. I will take that report and see if we need to change our laws to make sure it never happens again," he said.
"At the end of the day, you can't have people enforcing the law taking it into their own hands for political purposes."