To Cross the Rubicon.

In ancient Rome, it was illegal for a provincial governor to lead his army into Italy without the Senate's permission. 

The Rubicon River was the boundary between Italy and the province of Gaul, where Julius Caesar, serving as governor of Gaul, was with his army.

In 49 BC Caesar crossed the Rubicon with his legions, defying the law and triggering a civil war which ultimately led to Caesar becoming dictator for life.

In 2025 Donald Trump, President of the United States of America, sent his legions, the National Guard and elements of the United States Marine Corp, to perform  law enforcement in California in direct contravention of the law, which would need there to be, not merely civil disturbance, but an armed insurrection against the United States of America to justify the deployment of Federal Troops, which there was not.

In 49BC Caesar's action triggered a civil war with Caesar becoming dictator for life - the parallels between Trump's actions and those of Caesar are uncanny, and deeply disturbing.

Those who fail to learn the lessons of history are doomed to repeat its mistakes.