Owning a number then is forbidding everyone to know a certain number. How ridiculous.
There already exists
illegal primes, which forbid everyone to know a certain number. Further, you can represent any piece of information as a number. If I take some illegally obtained top secret document and represent it as binary, for example, then that number would also be illegal.
Otherwise it is not decentralized.
There is difference between owning coins and owning the network.
The day comes, when access is gone. It's a matter of time.
Sure, but that doesn't make it any less theft if someone stumbles across my private key and empties my wallet.