Should Contracts Made Under Duress be Enforceable?
You prefer paying a hundred dollars to being killed, he prefers receiving a hundred dollars to killing you. It occurs to you that even a contract made under duress produces benefits for both parties and so should be enforceable. What’s the problem?
The problem is that making such contracts enforceable makes mugging more profitable, and so makes it more likely that you will be offered similar bargains in other dark alleys in the future. Whether contracts made under duress ought to be enforceable depends, economically speaking, on elasticity at the two margins. Where making the contract enforceable results in a large increase in how often duress occurs but only a small decrease in the damage done each time–almost certainly the case in my mugging example–we are better off if such contracts are unenforceable.
A few hundred years ago, prisoners of war were routinely asked to give their word not to try to escape and then permitted to wander around unguarded. Sometimes the prisoner was even permitted to go home, having promised not to rejoin his army until he had been exchanged for a prisoner of equal rank from the other side. A prisoner who violated his parole had proved that he was not a gentleman and treated accordingly by people on his own side. The parole system made war somewhat less costly for both sides and so presumably increased the amount of war, but it seems unlikely that the effect was very great. It substantially decreased the cost born by captive and captor. Its eventual breakdown during the Napoleonic wars probably made the world a worse place.
For a similar tradeoff in a different context, consider the question of whether Augusto Pinochet ought to be tried for crimes he was accused of committing while dictator of Chile. Enforcing the terms of an agreement that immunizes an ex-dictator from prosecution makes it less expensive for dictators to commit crimes while in power. But refusing to enforce the terms of such agreements makes it more expensive for dictators to give up power. Pinochet is one of the rare examples of a dictator who voluntarily relinquished power to an elected government. If his reward is a jail cell, the next dictator may not make that mistake.
In all of these cases, the agreement was made under duress: the threat of killing you, of keeping a prisoner of war locked up, of keeping dictatorial control over a country. The same is true of a peace treaty—threatening to drop bombs on someone until he agrees to your terms is about as clear a case of duress as one can find. Yet most of us feel as though it is a good thing for treaties to be kept, in part because, in a world where a treaty is only a piece of paper, it is hard to end a war short of annihilation of the loser.
Science fiction readers may want to consider the reaction of the aliens in Footfall, by Niven and Pournelle, to individual humans who surrender and then violate their "parole."