Before Attorney General William Barr completed his two days of Capitol Hill hearings this week, lawmakers should have secured an answer to this fundamental question about his work: Did he prematurely shut down Special Counsel Robert Mueller's investigation of the president?

It would be quite a surprise if Barr's answer was anything but no. He tends to make nice with Congress when he sits for questions from its members and he would have no doubt told them that Mueller and he agreed that the probe had reached a natural conclusion. But the fact that his elected overseers and the public can so far only guess at Barr's role in the closing of Mueller's shop is a measure of how thoroughly he has shrouded the work of the team over the past three weeks and how strong a hand he has to play in the expected upcoming wars over how much of Mueller's final report is released and how much redacted.

Besides, it is not a great leap to imagine that Barr did shutter the investigation. It is, he would surely tell you, within his rights to do so.

Six days after Barr was sworn in on Feb. 14, a possible clue to his role arrived in a CNN exclusive. The story was widely interpreted as Mueller having decided his work was done, and as time passed without further confirmation from other media outlets, the report came to seem premature. But the reporters' actual wording had been that Barr, not Mueller, was preparing to announce the end of the investigation within a week. If Barr had initiated talk of ending the probe and Mueller resisted, this is how the news likely would have come out. The action, and the leak about it, would have originated in Barr's office. The subsequent delay could have been caused by Mueller pushing for adequate time to tie up loose ends he hadn't expected to be dealing with so soon.

The scenario does not require that Mueller grossly capitulated. Large sections of his final report were probably already written and he may have argued fiercely for his right to pass his findings to other federal prosecutors and to submit on paper all of his findings and conclusions. But the by-the-book ex-Marine also may have accepted that Barr had every right to demand that he bring the probe to a close, abandon all new trails that had grown out of the initial investigation, and, for now, say nothing more.

Barr would not have to be a very clever lawyer to assert such authority. The special counsel regulations, written in 1999 in the wake of the impeachment effort that grew out of Kenneth Starr's investigation of Bill Clinton, casually entrust all power over special counsel investigations in the attorney general, an appointee of the president. The regulations do not explicitly state who decides when a special counsel investigation is over, but the attorney general decides when a special counsel investigation is necessary, appoints the special counsel, sets the boundaries on the investigation, and oversees every aspect of its operation. Of course he or she can say it's over. The special counsel has no power not invested in him by the attorney general.

So of course the attorney general can say the investigation is over. The special counsel has no power independent of the attorney general.

This is a foolish arrangement. Imagine a scenario in which a corrupt president becomes the subject of a federal criminal investigation. Because it would take precedence over any congressional investigation, the criminal probe, led by the president's handpicked attorney general, could all too easily be used to delay or totally prevent any meaningful investigation of the president. A congressional probe might only begin if at least one chamber were controlled by the opposition party. Two years or more could pass with a criminal in the White House and the public fooled into believing that an independent representative of their interests was working to fully expose any evidence of high crimes or misdemeanors.

How long, I wonder, would it be before Americans realized the attorney general controls the whole game?

On any given day, that presidential appointee, no matter how new to the job, could narrow the scope of the investigation, declare its work finished, and fulfill the office's obligations to Congress by reporting only the findings related to the investigation's newly narrowed scope. The president could be cleared of crimes wholly distinct from the ones he was suspected of committing, and that's the only information the public would get. The rest could be withheld on the grounds, established in the special counsel regulations, that the interest of protecting innocent civilians and public servants justifies a blackout.

Barr's behavior suggests that the hypothetical cannot be ruled out as the scenario that unfolded. We know CNN's report of the probe's completion came six days after his arrival in office. That makes sense if Barr was the decision-maker, and it fits with the Trump administration's history as a source of media leaks.

Next, we know that on March 5, Barr and Deputy Attorney General Rod Rosenstein met with Mueller to discuss wrapping up the investigation and were, according to Barr's camp, surprised to learn that Mueller would not be issuing a finding on whether President Trump committed obstruction of justice. That may be true, but one of the ways Mueller's decision makes sense is if Barr had recently given him no better choice.

We know too that one of the only crimes Barr has been able to say the Trump campaign was cleared of by Mueller — aiding Russian hackers in stealing emails from the Democratic National Committee or the Hillary Clinton campaign — was the same offense Trump's personal lawyer, Rudy Giuliani, had singled out as the sole activity that could be considered criminal. And it was, all along, among the most unlikely of possible offenses. Because really — Russian spies couldn't hack with DNC without the help of Donald Trump Jr.?

And we know that Barr was hostile to the entire Mueller effort in the famous 19-page memo he wrote last June. He has surely known for months that, once in office, he could halt Mueller's work and control the narrative around it for weeks, possibly dealing a fatal blow to any congressional attempt to recapture the momentum needed for impeachment.

We can hope congressional subpoenas will force out Mueller's full report and testimony. We can hope he has handed off enough of the case against the president to various U.S. attorneys offices and that, by some miracle, those appointees of the same president will have enough independence to file any indictments that are warranted. We can hope they'll somehow escaping the fate of former FBI Director James Comey and the rest of the FBI's January 2017 leadership.

But even if those hopes pan out, we have to learn that the special counsel regulations are idiotic. Until they're rewritten — until they require substantial reporting by the special counsel to Congress — we have no reasonable means of holding a president or his administration accountable for any crimes they might commit.