I too have had a few inquiries from California Businesses and have told them that they would require Canadian presence to own a .CA domain name.
Funny when one wanted me to be the admin and continue to own the domain. But I refused, as it was not worth for a couple of thousand dollars, to run the risk of the consequences of allowing them to do business under my name, when I had no clue whatsoever, what they would be selling. It was a three char domain and they could have been doing anything with an acronym they come up with.
As Frank said, it would be our moral obligation to do so.
I’ve completed many sales where I don’t actually know who the buyer is. They were completed at escrow.com and I’ve never had a hiccup. I’ve had one buyer tell me they are just trying to set up and meet Canadian presence requirements after payment during escrow. I just assume people have done their due diligence.