Candidate Donald Trump railed against what he calls the "dishonest media." Now President Trump will have to decide whether to do something about it.

Trump has already called for tougher libel laws and has threatened to sue newspapers. While it will be hard for President Trump to take direct action that makes it easier to sue or silence news outlets, his appointees will preside over federal agencies, including the Federal Communications Commission, that oversee media ownership. The Justice Department can block industry mergers, issue subpoenas to news organizations and obtain search warrants.

Perhaps more importantly, Trump is challenging the legitimacy of traditional media at a time of low public standing and great financial stress for the industry, especially newspapers. In September, a Gallup poll found that just 32 percent of Americans have a "great deal" or "fair amount" of trust in the media, the lowest level in the poll's history.

"The biggest influence Trump has is to continue to undermine the core function and credibility of the press," said Kelly McBride, vice president of academic programs at the Poynter Institute, a journalism nonprofit. "Everything the media does is based on the notion that it has relevance. The whole business model falls apart if you're irrelevant."

Trump's campaign pushed to discredit media outlets in the eyes of his supporters. He dismissed critical stories as lies and barred reporters from covering his rallies. He threatened to sue the New York Times for reporting on two women who claimed he groped and kissed them without consent. He didn't rule out suing NBC over the leak of the infamous "Access Hollywood" tape.

"We're going to open up libel laws and we're going to have people sue you like you've never got sued before," Trump said at a rally in February.

Yet Trump can't do much to weaken the nation's libel laws, said Floyd Abrams, a leading First Amendment lawyer. Those are enacted at the state level, and Trump would need to get states to amend their laws or get Congress to enact a federal law.

"I think he was simply unaware that there is no federal libel law," Abrams said. "We have 50 state libel laws and they're limited by the First Amendment. There really isn't much of a role for Congress, let alone the president."

Trump will have the power to appoint judges who are less press-friendly or are willing to challenge key First Amendment cases like Times v. Sullivan, a 1964 landmark Supreme Court case that protects the press from libel claims. Right now, there's one vacancy on the high court, and Trump will need Senate approval to fill it.

As president, he's free to sue the New York Times. But that could force him to reveal embarrassing details about his business interests, like his tax returns, Abrams said. He may also recognize that the First Amendment cuts both ways, said Jane Kirtley, a professor of media ethics and law at the University of Minnesota.

"Trump has benefited from First Amendment protection with his own attacks on a variety of people," Kirtley said. "It would be completely shortsighted" to weaken that.

Trump will have a harder time withholding information from the media as president. His administration will be subject to the Freedom of Information Act. And, unlike at his campaign rallies, President Trump won't be able to decide which media outlets cover his news conferences, since the White House press corps decides who gets credentials, McBride said.

"I'm not sure he'll fully grasp that he'll need to provide the press with information whether he likes it or not," Kirtley said.