^They do have authority over the sport in England, though. If Rafa Benitez criticises a referee at a press conference at Liverpool's training ground then they'll go after him. If they can do that then they can act against West Ham and Millwall.
Millwall fans have a reputation that, unfortunately, is well earned. There seems to be organised violence whenever they play certain teams which cannot be explained by local rivalries. Leeds and Cardiff are not local.
Portions of West Ham's support played in to this, however, but they played another team their fans hate - Tottenham - at home on Sunday without incident.
I have been to a number of West Ham games and have noticed a level of fan anger and hostility that I haven't seen when watching my own team or others.