In recent days, President Donald Trump has escalated his attacks on the FBI, and even people from his own party are getting concerned.

On Sunday, former GOP lawmaker Joe Walsh warned Trump that his attacks on the nation’s premier law enforcement agency are “gonna bite you in the ass.” And he’s right.

Trump’s tweets about current or former FBI officials could violate laws meant to protect witnesses, according to two former White House ethics lawyers.

In a series of tweets last week, Trump attacked former FBI Director James Comey, current FBI Deputy Director Andrew McCabe and outgoing FBI general counsel James Baker, accusing them of “political bias.”

In a tweet on December 23, Trump repeated a previous claim that Comey leaked a memo to a friend to pass along to a reporter. In the same tweet, the president accused McCabe of receiving $700,000 from “puppets” of Hillary Clinton. In a follow-up tweet that day, Trump added, “FBI Deputy Director Andrew McCabe is racing the clock to retire with full benefits. 90 days to go?!!!” And in a third tweet, he wrote, “Wow, ‘FBI lawyer James Baker reassigned,’ according to @FoxNews.”

Well, according to two former White House ethics lawyers, Trump’s attacks amount to “witness intimidation.”

The main federal law regarding tampering with a witness, victim or informant is 18 U.S. Code § 1512. Among other violations, the code calls for punishing “whoever knowingly uses intimidation, threatens or corruptly persuades another person, or attempts to do so” in order to “influence, delay or prevent the testimony of any person in an official proceeding” or “cause or induce any person to withhold testimony, or withhold a record, document or other object, from an official proceeding.”

As noted by Newsweek, the FBI and special counsel Robert Mueller are investigating Trump’s 2016 campaign, including whether Trump obstructed justice by firing Comey in May—and it’s possible that Comey, McCabe and Baker could be witnesses in that probe.

“Normally, someone being investigated for obstruction of justice who intimidates and threatens three key witnesses against him (here Comey, McCabe and Baker) risks additional witness tampering charges,” tweeted Norm Eisen, a senior fellow at the Brookings Institution and special assistant for ethics and government reform for former President Barack Obama.

Richard Painter, a professor at the University of Minnesota Law School who served as chief ethics lawyer in the George W. Bush White House, agreed, Newsweek reports.

“Using Twitter on Christmas Eve to intimidate a witness (McCabe) in a criminal investigation is not a very Christian way to celebrate the holiday,” he tweeted. “But it does make Mr. Mueller’s job easier and that’s a nice thing to do. Merry Christmas!”

Trump’s tweeting about former Acting Attorney General Sally Yates, whom he fired in January, might have also involved intimidation, Hannah Ryan has written for Just Security, a national security law and policy online forum.

The president has also attacked Attorney General Jeff Sessions and Deputy Attorney General Rod Rosenstein, both of whom could be witnesses to an obstruction of justice probe.

“He’s trying to affect the testimony of a witness, which you’re not supposed to do,” Peter Zeidenberg, a former federal prosecutor, told Newsweek.

It’s unlikely that senior law enforcement officials such as Comey and McCabe are easily intimidated. “Comey is the former head of the FBI and spent his career in law enforcement,” Renato Mariotti, another former federal prosecutor, told Just Security prior to Trump’s more recent comments. “In my nine years in law enforcement, I faced much tougher threats than that tweet.” ShareTweet