[kimixa]

I don't think it'd be illegal at all.

I think a number of people misunderstand that the reason why a lot of companies have a "Don't talk about why someone left" de-facto policy is because if there's any ambiguity it's probably not worth the cost of having to defend yourself from a possible libel lawsuit, and not that it's against any law.

The cost/benefit of that changes if there's no ambiguity, evidence of truth is after all a good defense against libel charges (in most sane jurisdictions...), and if the reason is "big" enough they may feel obliged to make it known.