The Richmond rally was originally planned as a protest against proposed state gun legislation but is expected to bring white supremacists, anti-government extremists and anti-fascists. Amid all of the soul-searching questions about race that officials in Charlottesville and other cities have wrestled with to try to stave off ugly confrontations, the 2017 report on the government response offered some concrete guidelines on security and communication.

Here are some ways that Richmond is trying to avoid a disaster on Monday:

The governor is banning guns, torches and even baseballs.

When Mr. Northam declared the state of emergency, he also prohibited civilians who approach the Capitol from carrying weapons. “Weapon” is broadly defined: Guns, bats and torches are included, as are laser pointers, scissors and baseballs. The ban and emergency declaration are in effect until Tuesday evening.

The move did not go unchallenged. The group that is hosting the event, the Virginia Citizens Defense League, fought Mr. Northam’s executive order in court, but the State Supreme Court upheld the ban.

Mr. Northam’s ban was one of several actions the authorities have taken in recent days that is in line with the recommendations of the post-Charlottesville report, in which a former federal prosecutor described in brutal terms the failures of officials there.

In 2017, a Charlottesville police captain asked a local prosecutor whether the police could ban bats, poles and other weapons from the park where white nationalists and counterprotesters had planned to gather. The prosecutor said no, and the Charlottesville Police Department prepared for the event under the belief that it could not enforce a ban on sticks, shields or any other potential weapon.