Termination suits often come down to image, especially of the employer's conduct. An employer that's cooperative and fair usually wins. An employer that seems dodgy (by, for example, firing someone on hearsay and not cooperating with proceedings against the person who supplied the information) is at risk, and looks bad even if victorious.
This is a very gray area of law, at least in practice. There are few termination cases that are clearly black or white. That's why severance packages and those hideous PIPs exist.
Firing someone without cause or even for a demonstrably faulty cause is not a tort, Michael.
I haven't seen this in law but I worked for a very large company in a "right to work" state and this is how they behaved in all things. If you were fired you would never be told why. If you called for a reference you would be told the length of employment and last position held. Nothing more. I don't think they went to all that trouble for no reason.
Black: firing those who intend to unionize, firing with discriminatory intent, retaliation (including against protected insubordination such as whistleblowing), firing people because of disabilities that can be reasonably accommodated, firing people because they disclose compensation (anti-unionbusting provision), firing people for making legitimate use of HR or internal-mobility processes (a subcase of retaliation), firing people in retaliation for opposing harassment.
Gray: firing people who fail socially (when there's a record, in the company, of allowing internal transfer), firing people for ethically justifiable (but not explicitly protected) insubordination, firing people whose health issues interfere with the job, firing people you don't like.
In the US, most Gray cases are not considered tortious. You're correct. The burden of proof is technically on the employee to prove that it's a Black case.
If he knows what he's doing, however, the employee can establish enough Gray-Blackness that the company will desire to settle.
Typical firing example: Bob doesn't get along with his boss, Mark, who suspects Bob would rather be on another team. Mark gives him shitty performance reviews and he's flushed out. Looks like a non-tortious Gray case; the performance assessments are inherently subjective, but there's nothing about this that entitles Bob to legal protection. Even an inaccurate performance review is non-tortious managerial incompetence, right? Well, it's not that clear. For one thing, most companies make performance reviews part of the transfer packet. Then, a negative review can be construed as harassment: interference with work performance. Part of the employee's job is to cultivate internal relationships and that makes it harder.
Let's say that the performance review happened on February 1, with Bob being fired on March 15. Bob establishes that, in fact, he met with Alice (manager of another team) on January 24. Bob was, in fact, discussing internal mobility. He has a chain of emails to prove what was discussed.
That's not an uncommon thing for people to do when they don't get along with a boss, nor is it uncommon for bosses to pre-emptively fire flight risks. Now, Bob has a legitimate case for retaliation. He was making legitimate use of internal mobility processes and trying to build relationships within the company, which can reasonably be considered part of his job description, and he was punished for it with a negative review.
If, as is typical, his performance reviews are part of the transfer packet, his negative performance review constitutes harassment insofar as it interferes (tortiously) with his relationship with Alice.
Bob's claim is much stronger, if he has the paper. If he emailed himself (because, after being fired, he's lost access to his work account) copies of the relevant documentation, he has enough paper to initiate a discovery process. Even that, most companies would prefer to avoid.
But your use of the word "retaliation" is also suspect. "Retaliation" in employment law means a demotion or termination in response to an exercise of other employment law rights, like a sexual harassment claim. You can't claim "retaliation" when your boss is an asshole and deliberately tries to screw you. In the US, absent a contract that says otherwise, your boss can do that.
Your white/black stuff looks reasonable, but I'm going to go out on a limb and say that your "grey" category is what you want employment law to be, not what it is. I'm just an employer though, not a lawyer.
At this point I'm settled on the notion that there is no interesting theory of law I was unaware of that would give the fired Pycon dev any leverage in procuring a severance. You can be fired for any reason, a bullshit reason, or no reason at all. He was. End of story.
Thanks for the discussion.