Unperformance

CONDITION […] is a restraint annexed to a thing, so that by the unperformance the party to it shall receive prejudice and loss, and by the performance, commodity and advantage; […]

We have seen that A has an 'equity to rescind', ie, the ability to petition the court of equity for an order of 'specific unperformance'. The question then is whether A can additionally effect a retransfer of the right themselves, without the aid of either the court or the defendant.