IN THE WAKE of President Donald Trump’s inauguration, the FBI assumes an importance and influence it has not wielded since J. Edgar Hoover’s death in 1972. That is what makes today’s batch of stories from The Intercept, The FBI’s Secret Rules, based on a trove of long-sought confidential FBI documents, so critical: It shines a bright light on the vast powers of this law enforcement agency, particularly when it comes to its ability to monitor dissent and carry out a domestic war on terror, at the beginning of an era highly likely to be marked by vociferous protest and reactionary state repression.

In order to understand how the FBI makes decisions about matters such…