Nearly 45 years after Richard Nixon resigned the presidency, there remains no evidence that Nixon had advance knowledge of the Watergate break-in, even as evidence that he was deeply involved in efforts to cover up the crime has only grown. If one accepts Attorney General William Barr’s reasoning in the letter he sent Sunday purporting to exonerate Donald Trump of obstruction of justice, perhaps we should consider a belated exoneration of the disgraced former president as well. But Barr’s reasoning should not be accepted, because it sits squarely at odds with settled law and amounts to an attempt to preempt Congress’ constitutionally assigned role to determine if the president has committed high crimes and misdemeanors.

In his letter, Barr stated that Special Counsel Robert Mueller had not found sufficient facts to establish a conspiracy between the Trump campaign and Russia to influence the election. Barr also indicated that Mueller found evidence that the president may have obstructed the investigation but did not reach a conclusion on that issue. For some reason, Barr felt compelled to offer his and Deputy Attorney General Rod Rosenstein’s view on that matter, asserting that seeking an indictment of Trump for obstruction would be contrary to Department of Justice policy.

According to Barr, because Mueller concluded that “the evidence does not establish that the President was involved in an underlying crime related to election interference,” it would be difficult to prove beyond a reasonable doubt to a jury that the president had a “corrupt intent” to interfere with a grand jury or other official proceeding. Barr’s argument thus suggests that if a subject of a criminal investigation avoids indictment for the underlying offense—whether it be insider trading, burglary, or election interference—he should not be charged with criminal liability for efforts to obstruct the investigation of the potential offense, either.

That is simply not the law. Proof of an underlying crime is not an element of an obstruction charge, and individuals are regularly charged with obstruction without facing criminal liability for an underlying offense. To take just one example, Martha Stewart was charged with obstructing an investigation into insider stock trading without facing criminal liability for her trades.

The attorney general’s position is not only flatly wrong; it’s dangerous. If Barr’s view was widely adopted by federal prosecutors, it would provide a truly perverse incentive to engage in obstruction. If wrongdoers knew they were unlikely to be charged with obstruction if prosecutors are unable to obtain sufficient evidence of an underlying crime, they would have every reason to engage in obstruction and witness tampering in an effort to prevent prosecutors from gaining access to underlying inculpatory testimony and other evidence that might lead to such charges.

Barr’s novel view on the intent required to prove an obstruction charge is not the only curious element of the attorney general’s analysis. Barr also asserts, without explanation, that there was insufficient evidence that Trump engaged in “obstructive conduct” with a “nexus to a pending or contemplated proceeding.” That is puzzling, given that there is ample evidence that Trump not only set out to influence investigations but, according to James Comey, even attempted to wholly shut down an investigation of his former national security advisor Michael Flynn (one that ultimately led to a guilty plea).

Barr’s own idiosyncratic views on the law may provide the answer to this puzzlement. Before joining the administration, Barr authored a lengthy memo criticizing Mueller for even pursuing an obstruction investigation of the president. As Barr opined, a president has plenary authority to stop or start a law enforcement investigation for any reason, including an investigation of the president’s own potentially criminal conduct. It therefore appears more than possible that the attorney general has concluded that Trump did not obstruct justice because the attorney general believes that presidents can’t be held liable for obstructing justice, even when they obstruct it.

A final mystery regarding Barr’s opinion regarding the Mueller obstruction investigation is why it was rendered at all. According to the attorney general, the special counsel did not reach a conclusion regarding whether the president should be criminally charged with obstruction of justice but limited his report to an elucidation of the evidence on both sides of the matter.

That makes a great deal of sense when one considers that, as Barr reiterates, there is a longstanding Department of Justice policy against indicting sitting presidents. Rather, the only remedy for criminal conduct by the nation’s chief executive so long as the president remains in office is impeachment by the House and removal by the Senate. Because the president cannot be charged, there is simply no charging decision to be made by the Department of Justice.

Mueller appears to have properly taken that policy into account. Because any opinion on whether Trump should be charged with a crime would be wholly hypothetical, he chose not to express an opinion. That is the same approach taken by Watergate special prosecutor Leon Jaworski, who, in his “road map” memorandum to Congress, transmitted the evidence he had compiled of Nixon’s involvement in an obstruction of justice scheme without reaching any conclusions on the president’s culpability, a matter Jaworski believed was properly assigned to the Congress.

The question, then, is why Barr felt the need to supplement Mueller’s account of the relevant evidence on the obstruction issue—none of which Barr detailed in his letter—with an answer to the entirely hypothetical question of whether the DOJ would seek to charge Trump if it could. One can’t help but question whether Barr’s letter amounts to an attempted usurpation of the constitutionally assigned authority of the House to determine whether the president engaged in an impeachable offense.

In any event, one thing is clear: Given the at best idiosyncratic and more than arguably outright wrong views of the obstruction of justice offense that appear to have informed Barr’s conclusion, it is all the more clear that all of the evidence regarding the president’s conduct adduced in the Mueller inquiry must be transmitted to Congress in connection with its investigation of whether Trump engaged in high crimes and misdemeanors.