Even Trump's Justice Department states that fact:
In a memorandum issued on August 2nd, Rosenstein spelled out the details of Mueller’s jurisdiction. He said that Mueller had the authority to investigate:
Allegations that Paul Manafort:
Committed a crime or crimes by colluding with Russian government officials with respect to the Russian government’s efforts to interfere with the 2016 election for President of the United States, in violation of United States law;
Committed a crime or crimes arising out of payments he received from the Ukrainian government before and during the tenure of President Viktor Yanukovych.
The second point shows Mueller’s authority to bring the case that he did against Manafort,
but the real news is in the first point.
That statement could not be clearer that Mueller can examine whether a member of the Trump campaign and the Russians were “colluding,” and thus working together “in violation of United States law.” In other words, according to Rosenstein, collusion would be a crime.
https://www.newyorker.com/news/daily...ion-is-a-crime