I looked through the website and it seems to me that the black list is a list of companies that engage in illegal activities (i.e. dumping waste in non-designated areas) or shady practices (i.e. not providing information to stock holders where the profits are going) and other things.
It's not a company specifically that could discriminate but the managers who do the hiring.
As far as I can tell, it looks like being on the black list just means that a company is "non-transparent" by their standards, in that given a list of questions about the company, from publicly available information, none of the questions could be answered either way.