I very much doubt whether a blacklist exists. From a legal HR perspective such a list would be a ticking time bomb for litigation. You'd have to screen the list regularly for gender, race and religious discrimination. You'd have to keep extensive notes on a peer review basis on why a person was on such a list. You would have to periodically review whether a name could be taken off the list.
Even following all best practice it would still be a highly unusual HR practice to establish an employment blacklist and its very existence would give the HR department sleepless nights.
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