Invalidating bitcoins would not work though. additionally, it is against the philosophy of bitcoin, basically to be a currency without supervising powers.
You literally have to think of bitcoins like real cash. I know that it feels unnatural at first, as usually everything you do software side on a computer is reversible, but that is not the case with the way bitcoins work. Everyone who runs the bitcoin client validates transactions and when a certain threshold is reached, the transaction is successful.
Therefore, to prevent the validation of transactions, you would have to run an astonishing number of clients which refuse validation.
The only way you could intercept stolen bitcoins at this point is, that the services which you can use to exchange bitcoins to dollars keep a db of stolen coins and prevent those from being cashed out.
You literally have to think of bitcoins like real cash. I know that it feels unnatural at first, as usually everything you do software side on a computer is reversible, but that is not the case with the way bitcoins work. Everyone who runs the bitcoin client validates transactions and when a certain threshold is reached, the transaction is successful.
Therefore, to prevent the validation of transactions, you would have to run an astonishing number of clients which refuse validation.
The only way you could intercept stolen bitcoins at this point is, that the services which you can use to exchange bitcoins to dollars keep a db of stolen coins and prevent those from being cashed out.