Deputy Attorney General Rod Rosenstein and other top Justice Department officials opened an obstruction of justice investigation into President Trump himself in the week after he fired then-FBI Director James Comey in an attempt to rein him in, according to a report published late Thursday.

At the direction of then-acting FBI Director Andrew McCabe, the DOJ secretly opened a probe into Trump because they were worried about his attempts to control other government operations, including his telling Comey to stop looking into his former national security adviser, Michael Flynn, CNN reported.

Trump's personal lawyer Rudy Giuliani said Thursday Trump had a legal right to fire Comey.

[Byron York: Ten questions for James Comey]

"It's shocking that the FBI would open up an obstruction case for the president exercising his authority under Article II," Giuliani told CNN.

The investigation started in the eight days between Comey's termination and special counsel Robert Mueller's appointment.

Rosenstein appointed Mueller on May 17, 2017, to lead the now-19-month-long deep dive into potential collusion between the Republican's campaign and the Russian government.

The Washington Post reported in 2017 that the DOJ had commenced its own research project into Trump.

As part of the discussions about how to rein in Trump, Rosenstein had offered to wear a wire while meeting with Trump, though he has subsequently said he was joking. He also reportedly proposed looking into whether Cabinet members would be willing to remove Trump via the 25th Amendment.