Supporting Routed Units in A Game of Thrones
One of the players in the game in question just sent me this link: http://boardgamegeek.com/thread/98106/supporting-routed-units


  Routed units have no combat strength. They still count towards a player s Supply limit, but if a routed unit is forced to retreat again in the same game turn, it is automatically destroyed. Routed units may never be taken as casualties in battle. Routed units may not participate in a march, even if a March order token is resolved at their new location. After all March orders have been resolved for the turn, return all routed units to their normal upright position.


It seems that the accepted interpretation is that routed units may give battle (with a strength of zero) and may be supported.