Illegal or not, this is power politics. Those with the money will rule.
What needs to be done is an intervention at the government level. The workers of Wal Mart have no say in the matter. They are disposible, and easily replacable. We have Canadian citizens all across the country looking for jobs, unionized or not.
If we want something done it has to be mandated by the government. Wal Mart is not going to listen to 200 crying employees.