Getting around downtown Chicago is a challenge at the best of times. Weekdays feature a constant flow of carefully and swiftly moving traffic; weekends all the more so. But it is a city of 2.5 million people, in a tri-state metro area of 9 million. Back in the days when Chicago was known as “The City that Works” – a generation ago, at least – the city fathers took great care to minimize any event that threatened to jeopardize that title. We had parades occasionally; we had demonstrations all the time. The Constitution guarantees American citizens’ right to such things....