The rule was very practical. The Romans understood the danger of allowing a large armed force to march on the capital city.  To allow this might spell the end of the republic. Best that popular conquering generals and their armies stay a safe distance away and respect the democratic institutions at the heart of Roman democracy.

Caesar broke the rule. He marched on Rome. He didn't care what the Senators thought. The rest is history. Within a generation, there was no republic.

The FBI has now taken similar action. It has signaled in the clearest possible manner it does not care what the people or their elected representatives think. It will do what it pleases, and the consequences be damned.

The recently released Durham report paints a graphic picture of an agency out of control. The FBI did not blunder into an investigation of Donald Trump, his campaign, and his associates. The FBI undertook to deliberately destroy Trump and those around him including General Flynn. The FBI took unto itself the power to decide who could be President.