Former Obama Justice Department official Eric Columbus took to Twitter Friday to point out some legal misconceptions about special counsel Robert Mueller’s Russia investigation, while lending his opinion on how and why the probe will end.

Daily Caller reports:

Eric Columbus, former senior counsel to the deputy attorney general under Obama, explained on Twitter why we should not expect any criminal charges against Trump, despite a growing chorus of pundits and Democratic politicians predicting that Mueller is building an obstruction of justice case. As Columbus points out, the law guiding independent counsel Kenneth Starr that allowed him to indict then-President Bill Clinton Starr’s investigation into the Clinton during the 1990s had expired in 1999 “amidst concern that ICs had too much leeway,” he writes. Mueller is a “special counsel,” the position that replaced independent counsels, out of concern that ICs had too much power, Columbus notes. In other words, Mueller “is essentially the equivalent of a U.S. Attorney, except that his jurisdiction is defined by topic rather than geography,” wrote Columbus. Therefore, Mueller reports to deputy Attorney General Rod Rosenstein because Attorney General Jeff Sessions has recused himself.

Columbus ends his 19-part thread by tweeting, “”Trump won’t be indicted, this is all about impeachment, the upcoming midterm elections are crucial, Rosenstein remains a very important guy, and I’m holding my nose and hoping that Sessions stays where he is.”

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Mueller almost certainly won't indict Trump – not because it would be unconstitutional, but because Mueller's authority is very different from Ken Starr's was. I can explain. 1/https://t.co/BoZHbz0OFm — Eric Columbus (@EricColumbus) January 26, 2018

As @waltshaub notes, DOJ's Office of Legal Counsel — in essence, the lawyers' lawyers — has opined that it's unconstitutional to indict a sitting president. OLC reached this conclusion twice — in 1973 and in 2000. Here's the 2000 opinion: 2/https://t.co/SwBLJCbLOd — Eric Columbus (@EricColumbus) January 26, 2018

Last year @charlie_savage discovered that in 1998 Ken Starr solicited an opinion from a highly regarded law professor, @rrotunda, who reached the opposite conclusion. 3/ https://t.co/nfeILzcIwR — Eric Columbus (@EricColumbus) January 26, 2018

Even though Starr ultimately decided not to indict Clinton, he concluded he *could* do so. 4/ https://t.co/16VCKCYSNR — Eric Columbus (@EricColumbus) January 26, 2018

Why did Starr feel he could ignore OLC's 1973 opinion? Because the law under which he was appointed allowed him to do just about anything. His title was "independent counsel," and for all intents and purposes he was the Department of Justice with regard to Clinton. 5/ — Eric Columbus (@EricColumbus) January 26, 2018

That law expired, however, in 1999 (existing independent counsels were grandfathered in) amidst concern that ICs had too much leeway. It was replaced by a much tamer system allowing for the appointment of a "special counsel" — which is Mueller's title. 6/ — Eric Columbus (@EricColumbus) January 26, 2018

Mueller is essentially the equivalent of a U.S. Attorney, except that his jurisdiction is defined by topic rather than geography. He reports to Deputy Attorney General Rod Rosenstein, who is the acting Attorney General for such purposes due to Sessions' recusal. 7/ — Eric Columbus (@EricColumbus) January 26, 2018

(If Sessions leaves, Trump can immediately name any Senate-confirmed official to serve as acting AG for nine months — e.g. EPA head, and former Oklahoma AG, Scott Pruitt, who could then try to restrict Mueller's running room. This is why I hope Sessions stays on the job!) 8/ — Eric Columbus (@EricColumbus) January 26, 2018

Per the DOJ special counsel regulations, Mueller must abide by all DOJ "rules, regulations, procedures, practices and policies." (28 C.F.R. 600.7(a), if you're keeping score at home.) 9/ — Eric Columbus (@EricColumbus) January 26, 2018

And Rosenstein may veto any Mueller action he deems inappropriate or unwarranted. 28 C.F.R. 600.7(b). 10/ — Eric Columbus (@EricColumbus) January 26, 2018

By contrast, the independent counsel statute allowed Starr to deviate from DOJ policies where necessary to achieve the purposes of the statute, and didn't allow the Attorney General to restrict his actions (other than firing him for good cause). 11/ — Eric Columbus (@EricColumbus) January 26, 2018

Given these rules, it's extraordinarily unlikely that Mueller would bring a prosecution that, in the judgment of DOJ's Office of Legal Counsel, would violate the Constitution. 12/ — Eric Columbus (@EricColumbus) January 26, 2018

(Theoretically, Mueller or Rosenstein could ask OLC to revisit its opinion, but it’s very doubtful that OLC would change its view on an issue that it already addressed twice.) 13/ — Eric Columbus (@EricColumbus) January 26, 2018

So what can Mueller do if he believes that Trump has committed criminal acts? Mueller must provide Rosenstein a final report explaining all his "prosecution or declination decisions" — i.e. why he prosecuted individuals or declined to do so. 14/ — Eric Columbus (@EricColumbus) January 26, 2018

The format of this report isn't specified by regulation, but if Mueller were otherwise inclined to indict Trump, I suspect he would set forth relevant facts. I also believe Rosenstein would make relevant portions of the report public, although he isn't obligated to do so. 15/ — Eric Columbus (@EricColumbus) January 26, 2018

While some have suggested that Mueller would make an "impeachment referral" to Congress if he finds evidence of impeachable acts, that was part of the now-expired independent counsel statute and is no longer an option for Mueller. 16/ — Eric Columbus (@EricColumbus) January 26, 2018

Other than judicial filings and trial proceedings, Mueller's work can reach Congress only with Rosenstein's blessing — unless Congress subpoenas Mueller's report, which isn't likely to happen as long as the GOP controls Congress. 17/ — Eric Columbus (@EricColumbus) January 26, 2018

(It's also possible that Congress might subpoena grand jury evidence, as suggested here by @rgoodlaw and @alexgwhiting.) 18/ https://t.co/kkUOBja0Dy — Eric Columbus (@EricColumbus) January 26, 2018