I completely disagree. I own the bitcoins in my wallet just as much as I own my plot of land according to county records or the dollars in my bank account according to my bank. It doesn't matter that the blockchain is made public. If someone stole my password to my bank account, they might have access to my funds, but that doesn't give them a right to my funds. Neither would the theft of my private keys give them a right to my bitcoins.
You can disagree, of course, but in both your examples (land ownership and bank account) there is a third party keeping independent records about who is the rightful owner. There is no third party in bitcoin, If you have the private key you have the bitcoin. This is why in bitcoin the private key IS the right!
If the rightful owner can be proven, however, then there would be a case against the one who has stolen the funds. Rightful ownership could potentially be proven by showing a transaction with another person. For example, if I sold a laptop to someone, and they sent the funds to 18tkn, then I could prove that those funds sent to 18tkn do indeed belong to me.
I guess the argument you are attempting to make is that a court couldn't determine who stole from who, or who originally owned the private key. I'd say that some sort of "first use" doctrine could become a standard for that sort of determination. If I can prove that I used a particular address before someone else, then I am the proven owner of that address.
It might be illegal but theres nothing you can do if someone takes your coins. If the only excuse to have a state is to enforce property law what point is the state if that is impossible ?
Illegality is a moot point without enforceability and if people know they can get away with something it will brinng out the worst in humanity.
What are you talking about? The court could order them to pay me, and that's that. If he refuses, and his wallet is password protected or otherwise inaccessible to others, then he stays in jail until he changes his mind.
The argument might be true that you cannot force a person to send Bitcoins back to their rightful owner if they have a strong password on their wallet, but you can certainly "encourage" a person to do so, and that's a far cry from "there's nothing you can do".
It is easy to leave no trace when stealing bitcoins, there will be no one for court to prosecute. Of course you can sacrifice liberty and make every transaction traceable to a person, but the side effects of the cure will be worst then the disease.
Again, that is a far cry from "there's nothing you can do". It's like saying there's nothing a store owner can do when someone steals cash from their store. Well, sure, they have a lot they can do. They can look at the evidence (fingerprints, security camera footage, etc), potentially find the perpetrator, and prosecute them. Same thing if someone steals your Bitcoins - look at the evidence, find the perp, and prosecute.
If the perp is good at covering their tracks (which most are), THEN there's nothing you can really do, but saying there's nothing you can do as a catch-all to all Bitcoin thefts is plain wrong.