Fired FBI Director James Comey has emerged as the main figure in what some Democrats believe will be an obstruction of justice case against President Trump in the Trump-Russia matter. Comey’s stories of conversations with the president, plus the fact that he was fired, ostensibly as a result of the Russia probe, make him potentially the star witness in the case.

Which brings up an intriguing legal question. Comey is a good friend of special counsel Robert Mueller — such a good friend, for about 15 years now, that the two men have been described as “brothers in arms.” Their work together during the controversies over Bush-era terrorist surveillance has been characterized as “deepening a friendship forged in the crucible of the highest levels of the national security apparatus after the 9/11 attacks,” after which the men became “close partners and close allies throughout the years ahead.”