The US Department of Justice is investigating the boycott of Trump events by TV channels from the presidential pool. Previously, he restricted their access to the White House

The US Department of Justice said it is investigating several US television networks for possible violations of federal antitrust laws over their recent suspension of joint coverage of President Donald Trump.

The department requested correspondence and other materials related to the White House television pool from ABC, CBS, CNN, NBC and Fox News. Under this system, TV channels take turns covering the president's activities and transmitting footage to other media outlets.

Last month, networks suspended the system for several days after the president banned CNN, MS Now and Politico from the White House.

Pool participants share their materials—photos and descriptions of the president’s movements—with other media.

“A collective boycott by commercial competitors may violate the Sherman Act,” a U.S. Justice Department official said, referring to a federal law that prohibits companies from engaging in monopolistic practices.

“The Antitrust Division is simply conducting an investigation to determine whether these news organizations violated antitrust laws,” the agency added.

Last month, Trump banned CNN, MS Now and Politico from the White House, accusing the outlets of publishing “fictions and lies” about his team.

The White House later restored their access after a court decision. Three publications have filed a lawsuit against the Trump administration, arguing that the restriction of access violates their First Amendment rights.

The First Amendment prohibits the government from restricting the freedom of the press. Courts have traditionally interpreted this provision as prohibiting authorities from discriminating against media outlets based on the content of their publications.

The Trump administration has taken a number of legal actions against news outlets in the US, including lawsuits over their coverage of the president.

In February, the White House announced it was taking control of the pool of journalists with access to Trump. For more than a hundred years, the work of this pool was carried out by the White House Correspondents' Association.