The last thing the world needs is more of Robert Mueller's commentary, but Congress is determined to have him hold forth at a public hearing.

It's not as though we don't already have the special counsel's version of events. He mustered enormous investigate resources and took two years to write a 400-page report that is available to the public and presumably carefully written (although not necessarily carefully thought through).

That should be enough for Mueller to stand on, and enough for Congress to make a decision to impeach or not impeach, or otherwise dispose of the matter as it sees fit.

Instead, Mueller is going to be asked to expand on his already-expansive report that not only blew through Justice Department regulations, but inverted the long-standing burden of proof in the Anglo-American legal tradition.

As a prosecutor, Mueller's job — his sole job, really — was to decide whether or not the president was guilty of a crime. He declined to do this, choosing instead to write a nearly 200-page volume on obstruction cataloging what he found in the course of not making the only decision he was supposed to make.

The relevant regulations say that 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."

On obstruction, Mueller reached no such decision, and he didn't write a confidential report, either — his report was clearly meant for public consumption. Besides that, he's a stickler for the rules.

"Mueller's action," Jack Goldsmith of Harvard Law School writes at the website Lawfare, "seems inconsistent with what the regulations tried to accomplish, which was to prevent extra-prosecutorial editorializing."

Worse, as Trump's special counsel Emmet Flood set out in an excoriating letter, by stipulating that the evidence prevented him "from conclusively determining that no criminal conduct occurred," Mueller stood the presumption of innocence on its head.

By Mueller's standard, the prosecutor doesn't have to prove guilt — the target has to prove innocence. And if the target doesn't, he will be disparaged in a long-form quasi-indictment spelling out why he's not exonerated.

If anyone not named Donald J. Trump were subjected to this new prosecutorial standard, it would occasion widespread comment and — one hopes — consternation.

There is, no doubt, public value in Mueller's report, but he wasn't supposed to be a free-floating ombudsman or truth commission. If Congress wanted to create one of those and charge it with running down every lead related to Trump's alleged obstruction, it could have. Under the regulations, though, the special counsel is only "to exercise all investigative and prosecutorial functions of any United States Attorney."

Now, Congress wants Mueller to compound the offense by speaking publicly. It doesn't want facts from him. They are already in the report. It wants opinions and sound bites, especially any embarrassing to the president. Congress wants him to spend a couple of high-profile hours further "not exonerating" the president.

If Mueller had a proper understanding of his role, he would decline the congressional invitation, and perhaps write a letter giving his version of events regarding his interactions with Attorney General William Barr, which became such a flashpoint last week.

But the fact is that Mueller and Congress have a symbiotic relationship. For two years, Mueller was acting as, in effect, the lead counsel for an impeachment inquiry — bizarrely housed within the executive branch — while Congress wants to use his moral authority as a crutch at a time when it is vulnerable to charges of partisan overreaching.

This, too, is not supposed to be how the system works. But we are long beyond anyone caring. For a swath of the political world and much of the media, all that matters is that Mueller "not exonerate" Trump, and the more, the better, in whatever format or forum.

Rich Lowry can be reached via e-mail at comments.lowry@nationalreview.com.

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