[afinemonkey]

It depends, I guess. If what you're talking about is a disagreement between two parties about the object of the contract or its conditions, I don't see why you couldn't resolve it the same way you would with a paper contract. I don't know if any country's definition of contract is broad enough to include smart contracts, but you could possibly bring this to court, perhaps?

If the two parties can agree on a new stipulation of the (smart) contract, a new contract can be issued.

As an aside, this is painful, as a smart contract's address will usually be linked to some user facing application or just your own wallet.

A way to facilitate this is through the use of a proxy contract, which is a contract that exists only to forward instructions to a secondary contract (the main one). The main contract can then do whatever is meant to do.

Now if there is a disagreement or a bug, after an agreement is reached, you can deploy your new contract, change the address on the proxy contract and you're done.