As one of the co-authors of an amicus brief challenging President Donald Trump’s appointment of Matthew Whitaker as acting attorney general, I believe that Whitaker’s appointment as a “department head,” bypassing the Department of Justice’s Senate-confirmed officers, violates the appointments clause of the Constitution. That has not stopped Whitaker from taking the job. With this power, Whitaker could obstruct the Russia investigation in many ways. The glaring legal problem for Whitaker—in addition to the illegitimacy of the appointment itself—is that any step he takes to slow or impede special counsel Robert Mueller’s investigation potentially could lead to an obstruction or bribery conspiracy charge against him, even if an attorney general would ordinarily have the power to make such moves. In case he is ever tempted to obstruct the Russia probe on the president’s behalf, Whitaker would be wise to study the history of Nixon’s two attorneys general and six other lawyers indicted for participating in Nixon’s legal scandals and what became of them.

First, it’s important to understand what he can and can’t do in the job. Under the DOJ’s regulations, the acting attorney general supervising a special counsel would have the authority to fire that special counsel. This removal power is limited to good cause, but a hypothetical Trump crony looking to sabotage the special counsel might try to craft pretextual cause to issue a firing.

There are also less drastic measures such a crony might undertake to hurt the investigation. Under DOJ regulations, the Special Counsel “shall notify the Attorney General of events in the course of his or her investigation” and, “at the conclusion of the Special Counsel’s work, he or she shall provide the Attorney General with a confidential report explaining the prosecution or declination decisions reached by the Special Counsel.”

Other Watergate lawyers also went to jail for conspiring in Nixon’s efforts to obstruct justice.

Thus, the attorney general could keep such a report confidential, essentially to cover up its findings. This might explain why Mueller has been relying on detailed criminal information filings to accompany indictments and guilty pleas to tell the story of the malfeasance of Trump officials. Some have further suggested that Trump appointed Whitaker so that he could reject indictments of his son Don Jr., his son-in-law Jared Kushner, and his informal adviser Roger Stone, among others. Others have expressed concern that Whitaker might defund the investigation. There was also initially speculation that he might try to spy on the investigation’s grand jury evidence, but there is consensus that Whitaker cannot unseal any sealed indictments.

Whitaker could theoretically block guilty pleas as well, but he did not block last week’s plea for lying to Congress by former Trump attorney Michael Cohen, even though the Washington Post reported that he was notified of it.

So far, then, it appears that Whitaker has not sought to interfere with Mueller. That would be wise. If he were to work against the investigation, Whitaker could be putting himself in infamous company: indicted attorneys general and government lawyers who aided Nixon’s crimes.

The last century has been full of crony attorneys general, but Nixon’s were the worst until Trump’s. As Nixon’s campaign manager prior to becoming attorney general, John Mitchell allegedly was involved in the back-channel sabotage of the 1968 Paris Peace Accords. When Nixon won, he persuaded FBI Director J. Edgar Hoover not to conduct a background investigation of Mitchell as his nominee. After three years as attorney general undercutting civil rights and civil liberties, Mitchell resigned to become director of the Committee to Re-elect the President, was ultimately implicated in the Watergate break-in, and was eventually convicted of perjury and served 19 months.

Nixon’s second attorney general was Richard Kleindienst. As deputy attorney general, Kleindienst had cooperated with a criminal conspiracy before Watergate. Nixon and his adviser John Ehrlichman told Kleindienst to drop an antitrust case against manufacturing and telecoms conglomerate ITT, one of Nixon’s biggest campaign donors. Kleindienst settled with ITT on implausibly generous terms and later lied to Congress about it. Kleindienst eventually resigned as the Watergate scandal escalated and in 1974 pleaded guilty in connection with the ITT case and received a sentence of 30 days in jail, which was ultimately suspended. If he abuses his power, Whitaker might end up being seen as comparable to Kleindienst: a relatively unknown lawyer who compromised himself legally to serve a president after having been promoted because of his own weakness and vulnerability.

Other Watergate lawyers also went to jail for conspiring in Nixon’s efforts to obstruct justice. John Ehrlichman, Nixon’s counsel, was found guilty of obstruction, perjury, and conspiracy in the burglary and then served 18 months. Ehrlichman’s aide, Egil Krogh, had approved the burglary of Daniel Ellsberg’s psychiatrist’s office after the release of the Pentagon Papers, and Nixon’s special counsel Charles Colson also helped organize that crime. Krogh was sentenced to two to six years, served 4½ months, and was disbarred. Colson pleaded guilty to obstruction of justice and served seven months.

John Dean, Nixon’s White House counsel, was convicted of obstruction of justice and was sentenced to time served (four months). Nixon’s personal attorney, Herbert W. Kalmbach, raised campaign funds illegally for legally questionable dark political ops. Kalmbach served six months in jail and lost his law license. Last but not least, G. Gordon Liddy, a former FBI agent and former prosecutor, organized the Watergate burglary itself and served more than four years in prison.

How might Whitaker find himself joining this lengthy list of lawyerly ill repute? If Whitaker had an arrangement with Trump to take the position in order to impede Mueller, he could be in jeopardy for conspiracy to obstruct justice. Whitaker’s potential personal legal troubles, though, raise the possibility that he might abuse his powers for his own benefit. Whitaker was on the board of World Patent Marketing, a company reportedly under investigation for fraud. The Federal Trade Commission alleged the company was operating “a scam that has bilked thousands of consumers out of millions of dollars.” There have been some questions raised as to whether Whitaker has been forthcoming and cooperative with the FTC. Whitaker rebuffed the FTC’s subpoena efforts last year, and now the FBI—over which the attorney general himself has oversight—is conducting a criminal investigation into the firm.

All of this raises suspicions about potential motives to do Trump’s bidding. If Whitaker intervenes in the Mueller probe to protect Trump, his work with World Patent Marketing and any possible conversations he had with Trump about helping each other would come under intense scrutiny for obstruction or quid pro quo bribery (official acts in return for something of value—here, impeding investigations). Further, just as a president ordinarily has the power to remove an FBI director at will, firing Mueller (for cause) may be technically within Whitaker’s power, but doing so with the “corrupt purpose” to impede a looming criminal investigation would constitute obstruction of justice. If Whitaker fires Mueller with pretextual cause, he would run the risk of a criminal charge himself.

Whitaker could learn a lot from the eight Watergate lawyers who were found criminally liable. Some took more active roles than others. Some were convicted only for obstruction and cover-ups. Some seem to have been pulled deeper into the conspiracy once they allowed themselves to be incriminated and compromised by a corrupt president. Whitaker has reportedly agreed to face questioning under oath before the House Judiciary Committee, and all of these issues will surely arise. As we witnessed last week with Cohen’s guilty plea, lying to Congress is a crime, so Whitaker must be honest in his answers. If he refuses to answer questions, citing some nonapplicable privilege, he could be subject to contempt of Congress, which could be enforceable by a citation to Mueller or the next attorney general, or by Congress acting on its own behalf. Any action Whitaker takes to interfere with Mueller potentially could lead to an obstruction indictment, sooner or later.

If Whitaker learns from the history of Watergate, his wisest move would be to resign and cooperate. Short of that, if he learns from his predecessor, he should simply recuse himself—and get a good lawyer himself.