As more details emerge about Donald Trump’s whistleblower scandal, it’s clear the man standing in the way of any investigation into the president’s actions, once again, is Attorney General William Barr. The House’s now formal impeachment inquiry may be the last remaining tool that Barr cannot tamper with.

Barr has already successfully stymied one investigation of presidential misconduct: special counsel Robert Mueller’s Russia probe. The attorney general released a misleading “summary” of the report before its publication, one that rankled Mueller himself. He also devised dubious legal standards to find insufficient evidence that Trump obstructed justice. Barr then prefaced the report’s release with an appalling press conference that painted Trump as the real victim. In congressional testimony, he trashed his own Justice Department to further defend Trump. Later, Barr took pains to hide the full Mueller report from Congress, deploying a baseless legal theory to conceal key redactions from lawmakers.

With each new development in the Ukraine scandal, we are seeing the Trump administration run the Barr playbook all over again. But there is an important difference. When Barr took the reins at DOJ, the Mueller investigation was near its end: Barr could not interfere with the probe itself; he could only run damage control once it concluded. This time, Barr has been in control from the start. And his Justice Department has blocked every avenue through which Trump might be held accountable.

Notes on the telephone conversation between Trump and Ukraine President Volodymyr Zelensky suggest Barr is implicated in Trump’s dirty work. (The memo is not a transcript but rather a compilation of “notes and recollections” from officials listening in.) Trump mentions his attorney general six times as a resource for Zelensky. The president urges Zelensky to investigate his potential 2020 rival Joe Biden—referring to unsubstantiated allegations that, as vice president, Biden used his position to quash a Ukrainian investigation into his son. “[W]hatever you can do with the Attorney General would be great,” Trump adds. He also told Zelensky that he would have his personal attorney Rudy Giuliani “give you a call and I am also going to have Attorney General Barr call and we will get to the bottom of it.”

Barr has been in control from the start.

The Justice Department released a statement Wednesday claiming that neither Trump nor Giuliani have spoken with Barr about pressuring Ukraine to investigate Biden and his son. But there is ample evidence that Barr played a substantial role in protecting Trump from a whistleblower complaint over the call. House Judiciary Chairman Jerry Nadler has already insisted that Barr recuse himself “until we get to the bottom of this matter.” House Intelligence Committee Chairman Adam Schiff also sent a letter to Barr on Wednesday saying the DOJ’s involvement “raises the specter that the Department has participated in a dangerous cover-up to protect the President.”

Before Barr’s possible involvement in the Ukraine affair had even been made public, the DOJ stepped in to mute the whistleblower complaint over this call. Under the Intelligence Community Whistleblower Protection Act, or ICWPA, whistleblowers in a federal intelligence agency must send their complaint to Michael Atkinson, intelligence community inspector general. The law tasks Atkinson with deciding whether the complaint is credible and of “urgent concern.” If it is, Atkinson must send it to acting Director of National Intelligence Joseph Maguire. ICWPA states that Maguire, in turn, “shall … forward” the complaint to congressional intelligence committees within seven days.

This process worked as intended—until the DOJ stepped in. Atkinson received the whistleblower complaint and found it to be a credible allegation of “urgent concern.” So he sent it to Maguire. Instead of sending it to Congress, as he was legally obligated to do, Maguire asked the DOJ’s Office of Legal Counsel, which makes law that binds the executive branch. The OLC declared that he could not pass it on in an opinion later released to the public in modified form, holding that the whistleblower complaint did not pertain to a matter of “urgent concern.”

This opinion is bizarre, because the law does not allow Maguire—and, by extension, the OLC—to overrule Atkinson’s assessment of a whistleblower complaint. It tasks Atkinson with deciding whether the complaint meets ICWPA’s standards, not Maguire. OLC claimed a right, on Maguire’s behalf, to independently determine whether the complaint constitutes an “urgent concern.” No such right exists.

The OLC then followed a different law, which requires executive branch officials to notify the attorney general if they discover potential “violations of Federal criminal law involving Government officers.” So instead of going to Congress, the whistleblower’s complaint went to the DOJ and, apparently, to Barr himself. The DOJ then assessed whether Trump may have committed a campaign finance violation, since it is a federal crime for any person to “solicit” any “thing of value” from a foreign national in connection with an election.

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On Wednesday, the DOJ released a statement announcing that the agency had determined that “that there was no campaign finance violation and that no further action was warranted.” It reached this finding by deciding that dirt on a political opponent is not a “thing of value”—disagreeing with Robert Mueller, who believed opposition research could qualify as a “thing of value.” The DOJ’s contrary conclusion theory of campaign finance law is far-fetched if not outright incorrect, ignoring the immense value that Trump and Giuliani evidently saw in a Biden investigation.

We don’t know for sure that Barr’s fingerprints are on this decision. But the OLC purported to follow a statute that required the whistleblower complaint to be “expeditiously reported to the Attorney General.” Thus, Barr was, at a minimum, presumably aware of the criminal referral. Moreover, there is no indication that Barr recused himself from the whistleblower matter, even though Trump invoked him on the call at the center of the affair.

In short, Barr’s Justice Department first manipulated ICWPA to prevent Maguire from sending the whistleblower complaint to Congress. It then manipulated campaign finance law to determine that Trump had committed no crime and refused to open an investigation. And the Attorney General himself, who appears to be implicated in the whistleblower’s complaint, almost certainly played a role in quashing any probe into the president.

Faced with this stonewalling at DOJ, House Democrats have no choice but to pursue impeachment if they want to get to the bottom of this scandal and punish Trump accordingly. Barr and his allies at the Justice Department certainly aren’t going to do it. To the contrary, the Justice Department seems eager to shield the president from any consequences. Under Barr, the DOJ has defended Trump’s refusal to comply with congressional subpoenas into his personal finances. It has even intervened on behalf of his former campaign chairman, convicted felon Paul Manafort, lobbying for him to receive special privileges behind bars. The Justice Department has all but announced that it will aide Trump’s allies and fight his enemies.

Barr will do whatever he can insulate Trump from federal law. We can certainly expect his DOJ to fight the House’s impeachment inquiry by attempting to stop executive officials from testifying, as it has before. But there is one important power that Barr lacks: He cannot stop Congress from concluding that the president has committed high crimes and misdemeanors.