The warbands rules were spread out across three issues of WD. GW has collected all the articles and put them into a PDF on their site you can find them here...
http://us.games-workshop.com/games/w...os/default.htm
The first download has the basic rules. The second download has clarifications to armies that allow them to function better in warbands and clarifications to warbands. This was where they changed the command models to only be allowed if you reach normal minimum unit size for the unit. I think they did this so as to prevent people from running around with a bunch of little three man command squads of tough as nails units like khorne chaos warriors and such.