File to have them show proof of quarantine.
If they don’t have it, they lied to the court.
Agreed. And that’s serious in its own right, if they haven’t informed you or are going out in public despite being “quarantined”.
There are apparently all sorts of legal exemptions and outs if you say you have COVID / quarantined. For example, there are freelancer sites letting you get out of contracts if you suddenly say “I have COVID! Can’t submit on time!”