When can an employee be blacklisted? How is it done? Is it legal?

I\'ve recently come across the concept of blacklisting candidates by employers. When can an employee be blacklisted? How is it done? Is it legal? Is it an industry database shared & managed by a centralized authority? How can we blacklist a candidate or remove him/her from that list?

Hi,
With reference to your query, you can ideally only blacklist candidates/employees on grounds of ethics and integrity ONLY, a situation where the same is substantiated (proven).
you may have a central repository within the organization and currently most organizations also do background verifications checks and police verification before hiring candidates.
To the nest of my knowledge there is no central authority as under the principles of natutral justice you cannot take away the rights for any individual to work or mar anyone's career.
regards,