President Donald Trump’s moves against impeachment witnesses may be illegal, whistleblower advocates say, but the President’s success in fending off Congressional and Justice Department investigations means the law, not Trump, is likely to come out worse from the confrontation.

On February 7, a crucial witness in the House Impeachment Inquiry last fall, Lt. Col. Alexander Vindman, was prematurely transferred back to the Pentagon from his position at the White House National Security Council. Vindman, Trump said in the Oval Office on Tuesday, “did a lot of bad things.” “We sent him on his way to a much different location,” Trump said.

Under the Military Whistleblower Protection Act, members of the armed forces cannot face retaliation for certain “protected communications,” including Congressional testimony. Transferring Vindman so soon after the President’s impeachment acquittal was “overt retaliation,” says Stephen Kohn, an attorney who chairs the Board of Directors of the National Whistleblower Center. “The transfer is not lawful,” Kohn says.

White House officials are pushing back on that line of argument. Vindman was expected to be winding down his tenure at the White House, National Security Advisor Robert O’Brien argued Tuesday. O’Brien said that the transfer of Vindman and his twin brother Yevgeny, who also worked at the NSC and raised internal concerns about Trump’s behavior, but did not testify in the inquiry, were just a routine culling of the White House staff. “It was just time for them to go back,” O’Brien said. “There is absolutely no retaliation with respect to the Vindmans as far as impeachment is concerned.”

The Pentagon has not yet commented on what exactly Trump meant by his comments, but Trump’s statements renew questions about the personal and professional security of federal bureaucrats who came forward during the impeachment inquiry and now find themselves incurring the wrath of an emboldened commander-in-chief.

Vindman, a 44-year-old Purple Heart recipient, was escorted out of the White House just two days after Trump’s acquittal in the Senate. Vindman had publicly testified in a high-profile appearance during impeachment proceedings that he was alarmed after hearing Trump ask Ukrainian president Volodymyr Zelensky to investigate former Vice President Joe Biden, a potential top political rival, and his son Hunter, during a July 25th phone call. “I was concerned by the call,” Vindman told lawmakers, noting that he had alerted the NSC’s attorney after listening in as a note-taker. “It is improper for the president of the United States to demand a foreign government investigate a U.S. citizen and a political opponent.”

Vindman was testifying to Congress under a subpoena; he had not come voluntarily. But his remarks drew the ire of both Trump and some of his allies in Congress, like Tennessee Sen. Marsha Blackburn, who questioned Vindman’s patriotism. When Vindman and his brother were removed from their positions at the NSC last Friday, Vindman’s attorney suggested the move was retaliatory. “Ltc. Vindman was asked to leave for telling the truth,” the attorney, David Pressman, said in a statement announcing his termination. “His honor, his commitment to right, frightened the powerful.”

Whistleblower advocates say the timing, and Trump’s own words, are clear evidence that the move was retaliatory, and part of a broader effort by the President to seek retribution in the aftermath of his acquittal. The day after Vindman was transferred, Trump attacked him on Twitter as “very insubordinate.” On Tuesday, just hours before O’Brien’s remarks countering the narrative about retaliation, Trump suggested that the military investigate Vindman.

“He is not trying to be subtle at all. He’s making a point. And that is a significant change for whistleblower protection,” says Tom Devine, the legal Director for the Government Accountability Project which has assisted thousands of whistleblowers.

The White House sees things differently. “The President,” O’Brien said Tuesday, “is entitled to a staff of people he has confidence in.”

Vindman’s attorneys did not respond to repeated requests for comment. But they are now unavoidably confronted with the question of what happens next. “There’s a pretty important threshold question… will Lt. Col. Vindman challenge that retaliation and if so, how?” said Irvin McCullough, a national security analyst for the non-profit Government Accountability Project.

The options for legal recourse though, carry more risks than rewards. Vindman could file a complaint with Glenn Fine, the acting inspector general for the Department of Defense, requesting an investigation into his removal, or Michael Atkinson, the inspector general for the intelligence community. Senate Minority Leader Chuck Schumer sent a letter to Fine on Monday requesting a similar investigation.

Daniel Meyer, who previously oversaw decisions on whistleblower cases for the Defense Department’s Inspector General, said it was crucial the department defend Vindman. “The uniformed leadership and the Defense Inspector General need to circle around this whistleblower and protect him,” he said. “This will also protect the President from his own instincts.”

But McCullough cautioned it is rare for an inspector general to investigate a sitting president. “Many IG’s are hesitant to ever investigate any matters that involve the White House,” he said.

Congressional committees could also probe the transfer as part of their oversight efforts, but Trump has shown that his White House will not comply with document requests. And having successfully avoided impeachment and removal for stiff-arming Congress, Trump is unlikely now to be more compliant.

The upshot is that the whistleblower protection laws, and whistleblowers themselves, will become more vulnerable in the wake of Trump’s actions. “This is a crossroads, for whistleblowers in particular, but for freedom of speech in general,” says Devine of the Government Accountability Project.

Which could personally cost Vindman, who as a non-partisan military official never sought the spotlight. Continuing to challenge the Trump administration could undoubtedly impede him, personally and professionally. “It’s a lot to ask for one man to take a stand for the entire U.S. accountability system,” said McCullough. “Its almost unfair to put that on Lt. Col. Vindman’s shoulders.”

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Write to Alana Abramson at Alana.Abramson@time.com.