Once it gets started, rioting is difficult to stop by authorities as constrained as American police forces are:
Of course authorities prepared to resort to brutality can terminate riots promptly. Buford gives the example of how the Sardinian police militia smothered a soccer riot during the 1990 World Cup matches. Hundreds of rowdy English soccer fans had flown in on chartered planes, and were determined to find trouble. The police did not try to cover every action node at once; this would have left them outnumbered everywhere. Instead, following textbook military strategy, they massed forces and surrounded first one, then another group of hooligans inglisi, rendering each in turn hors de combat by beating them senseless with truncheons. Few of the Englishmen actually had to be arrested (which would have been very time-consuming for the police). Nevertheless, because they were not allowed to innocently transpire through police lines to re-appear at some less well-defended action node, the riot soon collapsed.