In response to Manafort's motion for dismissal, this previously secret memo was revealed (with heavy redactions) expanding Mueller's scope of investigation.

Paul Manafort's legal team has forced disclosure of a troubling secret memo issued by Deputy Attorney General Rod Rosenstein that expanded the scope of the Robert Mueller's special counsel investigation beyond allegations of Russian election interference. Manafort's lawyers have moved to have his initial and the subsequent superseding indictments for business dealings years ago dismissed because, among other reasons, Mueller had no legal authority beyond probing Russian election interference in the 2016 election when he was appointed by Rosenstein on May 17, 2017.

The first and obvious question is, why on Earth was this kept secret? It smacks of secret police, not an open and fair investigation.

But there is another, truly serious problem that William A. Jacobson of Legal Insurrection explains in his excellent lengthy article on the memo:

By the time of the August 2 memo, Mueller already was investigating Manafort's business dealings and gathering evidence for an indictment (which would be unsealed less than three months later). On July 26, 2017 – a week before the Rosensten memo – Mueller's team raided Manafort's home, as the Washington Post reported on August 9, 2017: FBI agents raided the home in Alexandria, Va., of President Trump's former campaign chairman, arriving in the pre-dawn hours late last month and seizing documents and other materials related to the special counsel investigation of Russian meddling in the 2016 election. The raid, which occurred without warning on July 26, signaled an aggressive new approach by special counsel Robert S. Mueller III and his team in dealing with a key figure in the Russia inquiry. Manafort has been under increasing pressure as the Mueller team looked into his personal finances and his professional career as a highly paid foreign political consultant. Using a search warrant, agents appeared the day Manafort was scheduled to testify before the Senate Judiciary Committee and a day after he met voluntarily with Senate Intelligence Committee staff members. The search warrant requested documents related to tax, banking and other matters. People familiar with the search said agents departed the Manafort residence with a trove of material, including binders prepared ahead of Manafort's congressional testimony. The August 2, 2017 memo was classic boostrapping [sic]. It purported to confirm Mueller's authority to go after Manafort's business dealings, but Mueller already was doing that and had been doing it for weeks, culminating in the July 26 home raid.

The midnight raid on Manafort's home, waking him and his wife, was a shocking example of unnecessary bullying on its face intended to intimidate, not just to develop evidence. But the fact that it took place before the scope was even authorized, and that subsequent authorization took place in secret, absolutely stinks.

Mueller is earning the title of "rogue prosecutor," while Rosenstein is looking more like his accomplice than his boss.