I believe you could implement it in such a way that the coins involved are spendable, relying on "Pay to script hash": https://en.bitcoin.it/wiki/BIP_0016 https

I believe you could implement it in such a way that the coins involved are spendable, relying on "Pay to script hash": https://en.bitcoin.it/wiki/BIP_0016 https://en.bitcoin.it/wiki/BIP_0016