Exactly right. You're able to privately resell contract keys (and the buyer can then re-issue a new key with their delivery info, voiding the old one), but onionfutures.com doesn't facilitate it.

I mean, it kind of does, though, no? Since it is backing the contract in the first place? Why else would anyone buy those contracts if they didn't know they have value provided by onionfutures.com in the first place? Why can't I just sell a fake key, claim it'll work, and make unlimited money this way if that wasn't the case?

The specific laws do not actually ban the transfer of those contracts (tbf this is very complex and depends on your reading). And yes they do not facilitate the trading of the instruments in the secondary market but they absolutely facilitate the instruments themselves otherwise there cannot be a secondary market without any backers of the instruments.