Theory of Nullity: According to some scholars in the doctrine and the Swiss Federal Supreme Court (the 1988 Picasso decision), if one party is under duress, the contract is void for both parties. The right to invoke this nullity belongs solely to the aggrieved party. If the aggrieved party does not assert this invalidity within one year or does not consent to the contract, the contract is deemed invalid from the moment it was entered into.
The Theory of Rescission: According to this view, the contract is valid from the outset in the event of incapacity. However,
if the aggrieved party exercises the right of rescission, the contract is deemed void from the moment it was first entered into. If the party whose will was impaired does not exercise this right within one year, they cannot exercise it again.
Partial Invalidity: According to this view, in cases of defective consent, the contract does not bind the party whose consent was impaired. The other party remains bound by the contract. Again, the right to rescind the contract must be exercised within one year. Otherwise, after one year, the contract no longer binds the party whose consent was impaired.