Suppose, gentle reader, that in the city where you live there is a trial taking place, one that has attracted considerable attention and is fraught with potential for unrest should the verdict not conform with the expectations of some of your fellow citizens. Now suppose further that when the verdict is handed down, those same citizens are indeed so displeased that they take to the streets to express their outrage.
But you, gentle reader, busy as you are with commitments to work and family, have not followed the story closely. Now aware of the controversy, you decide to attend a protest rally near your home, not so much to protest yourself but merely to be educated on the issues.
And now suppose that some of the gathered protesters are worked up into such a state that they vent their anger by breaking the windows of some of the local businesses. The police, many of whom are present on the perimeter, announce that violence will not be tolerated, and to that end they proclaim the gathering to be an unlawful assembly, directing all who wish to avoid arrest to leave the area.