You don't receive legal documents when you mine bitcoin. You receive bitcoin locked to an address to which you presumably have the key. Good luck convincing everyone that it's your bitcoin when someone else can prove they have the key and you cannot.
Comments
Basically what you say is that if someone have keys from your car, its better proof that he owns your car, than legal documents ir court shows.
You don't receive legal documents when you mine bitcoin. You receive bitcoin locked to an address to which you presumably have the key. Good luck convincing everyone that it's your bitcoin when someone else can prove they have the key and you cannot.