Legally? There's not much in the "Customer First" plan, here is a selected quote under the heading of airport Access:
<font face="Verdana, Arial, Helvetica" size="2">......If customer movement from the aircraft to the airport terminal cannot be accomplished safely due to weather conditions(i.e., snow, high wind, heavy rain, etc) then such action shall be deferred until it can be safely accomplished......</font>
Looks like they can do whatever they want as long as it doesn't compromise "passenger safety" Customer First???? Yeah...right.