Then-FBI Director Robert S. Mueller III testifies before the Senate Judiciary Committee in 2013. (J. Scott Applewhite/AP)

After shifting the idea to the back burner for a few months, Congress seems ready to move forward on legislation providing more robust protections for special counsel Robert S. Mueller III. With the New York Times reporting on Tuesday that President Trump had pushed to dump Mueller last December — the second time he had actively sought to fire Mueller — it’s apparent that Mueller’s position may be more at risk than members of Trump’s party would like to think.

The proposed legislation, though, appears to leave open significant ways in which Trump could still derail the special counsel’s work — if it were even signed into law.

It’s worth a quick review of the existing boundaries and procedures for the special counsel. Mueller was appointed to his position last May by Deputy Attorney General Rod J. Rosenstein, acting in Attorney General Jeff Sessions’s stead, as Sessions had recused himself from any involvement in investigations into the 2016 campaign.

The statute allowing the appointment of Mueller gives him broad autonomy but includes a key check: The attorney general (or, in this case, the deputy attorney general) can demand that the special counsel explain “any investigative or prosecutorial step” — and can dictate that those steps not be pursued. The special counsel is also bound by the deputy attorney general’s delineation of what he can investigate. And the statute articulates that only Rosenstein (in this case) can fire Mueller and only for an articulated cause. Trump himself has no authority to do so. (There’s a line of argument that postulates Trump could argue that an inability to fire Mueller is an unconstitutional limit on his powers, an argument that would almost certainly end up being evaluated at the Supreme Court.)

What this means is that Rosenstein is as significant a point of leverage over the investigation as Mueller — if not more so. We dived into this Tuesday, noting that removing Rosenstein from his position — which Trump can certainly do — would allow Trump to slot someone in to manage Mueller to the president’s liking. The authority over Mueller stays with the deputy attorney general position, obviously. If that position is vacant, it falls to the solicitor general. But the Vacancies Act of 1998 allows Trump to fill Senate-confirmed positions (like deputy attorney general) with anyone who has already received Senate confirmation for another position. There’s a question about whether that process applies to positions vacated after someone was fired, mind you, but it seems likely that Trump could successfully argue that it does.

With all of that context, let’s consider the proposed legislation (as of Wednesday morning). The Post’s Karoun Demirjian reports that the bipartisan bill would mandate a 10-day waiting period after an order to fire the special counsel, during which period the firing could be appealed to a panel of three judges — and during which time no staff changes could be made to the special counsel’s team and no documents could be destroyed.

Now, in theory, this would be useful. If Trump were to order that Mueller be fired (or decide to risk the Supreme Court battle and declare him fired), the administration would have to make its case to that panel of judges who, presumably, would be fairly unlikely to agree with Trump’s move. No matter who’s serving in Rosenstein’s position, there would be a check on ousting Mueller.

As we noted on Tuesday, though, replacing Rosenstein gives Trump another way to interfere with the investigation. Remember: Rosenstein gets final say over prosecutions and areas of investigation. Replacing Rosenstein with someone willing to help derail Mueller would allow Trump to tie Mueller’s hands. The new deputy attorney general could simply block any new indictments or, as an expert told me, likely scale back the scope of the investigation in significant ways. Mueller would still be in place — he just wouldn’t be able to do as much. What happens at that point is anyone’s guess; investigations might end up getting kicked to other jurisdictions. But it would likely help Trump achieve his short-term goal: turning down the heat.

The other question with this legislation, of course, is: What happens when it gets to Trump’s desk? Is Trump going to sign a bill explicitly designed to keep him from taking an action he wants on Mueller? Uh, probably not. Could Congress override a veto? Doing so would take substantial support from Republicans on Capitol Hill, and given that Senate Majority Leader Mitch McConnell (R-Ky.) is on record saying this legislation isn’t needed, that seems unlikely.

As has been the case for some time, much of the protection of Mueller’s investigation depends on its being treated in good faith by the White House. Rosenstein clearly established the special counsel in large part to avoid meddling from the president — the entire point of a special counsel is that it’s outside of the normal chain of command to preserve its integrity.

The investigation into president Bill Clinton helmed by Kenneth Starr operated under the aegis of a now-expired law that established counsel completely independent of the executive branch. That law was inspired by president Richard Nixon’s successful push to fire the person responsible for the Watergate investigation. It lapsed in 1999 in part because Starr was seen as having too much autonomy, leading to the development of the current system.

It still has some loopholes.