I think what it means is that if I break your car and you sue me to get the money back from me, I can pay you in bitcoin and you'll have to accept it, i.e. cannot claim that I haven't repayed you for the damage. In all countries were Bitcoin is not an official currency (so pretty much everywhere) you could claim that even though I payed you in Bitcoin, it doesn't settle the debt and you reject the payment and ask me to pay you in an official currency.
That's like saying you can't pay one who doesn't have a bank-account. You can either give the money (or bitcoin) to some service that keeps them for this person and give them the access to it or find another way to do it. At this point, I'm pretty sure that the burden of proof goes over to the other person and they will have to show why they didn't work with you to get the money.
