Former White House press secretary Josh Earnest said on Sunday that it “may come as some surprise” to President Donald Trump that the president of the United States cannot in fact “unilaterally order” the surveillance of a U.S. citizen.

“This may come as some surprise to the current occupant of the Oval Office, but the president of the United States does not have the authority to unilaterally order the wiretapping of an American citizen,” Earnest said on ABC’s “This Week.”

“If the FBI decided to use their wiretapping authority in the context of a counterintelligence or criminal investigation, it would require FBI investigators, officials of the Department of Justice, going to a federal judge and making a case and demonstrating probable cause to use that authority to conduct the investigation,” he said. “That is a fact.”

.@joshearnest: This may “come as some surprise” to Pres. Trump, but a president can’t “unilaterally order the wiretapping” of a US citizen. pic.twitter.com/LdSc8VuliE — This Week (@ThisWeekABC) March 5, 2017

On Saturday, Trump claimed that President Barack Obama was “wire tapping” his phones at Trump Tower ahead of the 2016 election. He offered no evidence to support those allegations.

A spokesperson for Obama rejected that claim later the same day.

“A cardinal rule of the Obama Administration was that no White House official ever interfered with any independent investigation led by the Department of Justice,” Obama spokesman Kevin Lewis said in a statement. “Neither President Obama nor any White House official ever ordered surveillance on any U.S. citizen.”

Former Director of National Intelligence James Clapper said on Sunday that to his knowledge there was no FISA court order to implement surveillance on Trump Tower.

The White House nevertheless called on Sunday for Congress to investigate Trump’s allegations as part of its probe into Russian interference in the 2016 election.

“President Donald J. Trump is requesting that as part of their investigation into Russian activity, the congressional intelligence committees exercise their oversight authority to determine whether executive branch investigative powers were abused in 2016,” White House press secretary Sean Spicer said in a statement.