If that call led to you being fired you would have a good case to sue for damages from lost income.
I'm pretty sure it's illegal in the EU unless you provide explicit consent.
You don't have to break a law to be ruled against in civil court (in the US), but I agree with you; I don't see a case here (even checked with a lawyer who happens to be visiting.)
> You don't have to break a law to be ruled against in civil court (in the US)
Yes, you do; civil courts enforce civil law, which is actually law.
If you ask and confirm that they won't contact your current employer, then might it not fall under contract law?
... Yes that makes sense. No idea why I was thinking law == criminal law.