If it were possible to design a transaction type which was reversible (and fair) it could solve a lot of problems.
In version 1.0, when creating a UIA you will be able to specify an optional flag, which will allow the issuer to freeze or revoke any balance in that asset [1]. This is primarily to help gateways [2] comply with regulatory requirements. (Many governments want entities that hold user funds to be able to freeze / confiscate account balances.)
Crypto generally aims to let the end user own the value token
Which is why there's going to be inherent tension between reversible transactions and decentralized ownership schemes. In other words, if someone else can reverse a transaction and take tokens out of my wallet, did I ever really own those tokens in the first place?
Our solution is to provide both "traditional" irreversible tokens and "reversible" UIA's (where the UIA or their designee has the power to revoke anyone's balance). Since we also provide tools to allow people to trade them against each other, the relative market cap and value of the two different approaches will become clear.
[1] Actually, currently the plan is for all UIA's created post-1.0 to have these capabilities enabled, but allow the UIA issuer to permanently, irrevocably turn off the capability. This design is not final and may change before 1.0 is released!
[2] A "gateway" is a business that takes fiat currency deposits from the general public and issues a UIA; effectively shares of the UIA can be created or redeemed for an equal amount of fiat currency.