Kind of like driving down the road in your legally licensed 1990 Chevy pickup with valid plates and safety inspection . All at once a kid in a hopped up Honda Civic with an Acura engine crosses the center line and you wind up totaled.
Now the Honda driver's lawyer is saying if YOU had a newer truck with anti lock brakes the accident would have been avoided
This is what we have been saying when we talk about the risks involved with illegal modifications.
Yes it is hard to prove ,but all indications including controlling your plane ,another suspect crash and the illegal operation sure point in that direction. If his transmitter had been a type approved transmitter there would little cause for concern.
I doubt if you can force anything . I do know he would be removed from our club if he didn't pay up and agree to run only legal equipment in the future.
If it were my transmitter you would already have been paid