Concrete ways that Machiavellian managers can cause legal problems for their company
Unfortunately, most of the behaviors that Dark Triad managers have are considered perfectly legal, even though they can be very psychologically damaging. However, there are a few places that their behavior can cross the line into being legally actionable:
Lying — A lot of psychological harm can be done with just "stretching the truth" in a way that can't be addressed legally, because they sit in a gray area between truth and fiction. But sometimes the manager's behavior may be so bad that the law recognizes it as full-on lying.
Workplace bullying — Although this is a somewhat nebulous concept, due to recent developments in employment law, certain sustained patterns of behavior to be addressed in the legal arena.
Work sabotage
Withholding resources or information needed to do the job
Spreading lies or rumors
Relevant laws
There is no federal law that specifically targets workplace bullying. However, bullying done to a protected class (women, workers over 40, etc) becomes harassment, which is codified in federal law.
"Actionable harassment must be so severe or pervasive that it interferes with an employee’s ability to perform his or her work or changes the terms and conditions of employment."