Italian merchant cities bought out coastal lords' wrecking rights

Under the medieval custom known as ius naufragii (right of wreck), coastal lords along Mediterranean shores could legally seize the cargo, wreckage and even the crew and passengers, who were enslaved, of any ship that wrecked on their territory — a right some justified on the theological grounds that a shipwreck was divine punishment for a sinful crew, making its cargo fair game. The Viscounty of Léon reportedly sustained itself substantially on wrecking proceeds, drawing on the order of 100,000 solidi a year from the practice.

This custom created an obvious and dangerous incentive problem for Italian merchant cities whose ships regularly sailed past these coastlines: a lord who profited more from a wrecked ship's cargo than from one safely passing had little reason to help a struggling vessel, and in the worst cases had reason to actively lure ships onto rocks. Simply asserting a moral or legal claim that wrecking was wrong carried no force in a jurisdiction the Italian cities didn't control and couldn't compel.

Italian maritime republics negotiated treaties, trading trade access for guarantees to protect wrecked ships, offsetting the lords' incentive to let wrecks happen.

Lords rationally preferred wrecking income over safe passage, so moral appeals had no force.

Treaties gave lords something they valued more than wrecking revenue, removing the incentive.

As more cities signed, the custom lost economic rationale and faded by 1270.

When a counterparty profits from your failure, offset that incentive directly rather than demanding better behavior.

Through a spreading web of these treaties and accompanying legislation, ius naufragii had gone effectively out of practice across the Mediterranean by around 1270, ending a custom that had directly incentivized coastal populations against helping distressed ships.