Rhodian sea law made everyone pay for jettisoned cargo

A merchant ship of the ancient Mediterranean carried cargo belonging to many different owners at once, but only one captain who could act in an emergency. When a storm threatened to sink the ship, the fastest way to save it was to throw part of the cargo overboard — but that cargo belonged to specific merchants, not to the ship or the captain.

The Rhodians, whose trading fleet dominated the eastern Mediterranean by the first millennium BCE, did not try to prevent jettison or assign blame for it. Instead they wrote a rule about who pays afterward: if cargo is sacrificed to save the ship, every party whose property was saved — the shipowner and every other merchant aboard — must contribute to the loss in proportion to the value of what they had at risk.

Rhodian sea law made every party whose cargo was saved by jettison share the loss proportionally, so no one fought the captain's call.

The captain acts under time pressure, so rules governing the decision can't be enforced in the moment.

If the loss falls on one merchant, that merchant fights the call, causing delay and conflict.

Proportional sharing means each party's exposure is the same regardless of whose cargo is jettisoned, removing the incentive to contest.

After-the-fact accounting works because it only requires valuing property once the ship reaches port.

When one person must make a costly, time-pressured call that sacrifices shared assets, make all beneficiaries share the cost proportionally, rather than regulating the decision itself.

The rule outlived the civilization that wrote it: Roman jurist Julius Paulus cited Rhodian jettison law directly into the Digest of Justinian around 235 CE, medieval sea codes (the Rôles d'Oléron, the Wisby Sea Law) carried it into Northern Europe, and it survives today, essentially unchanged in structure, as 'general average' under the York-Antwerp Rules that still govern how marine insurers and shipowners split extraordinary sacrifice costs on modern cargo vessels.