There’s an ancient tenet of maritime law that is cropping up in reports about the catastrophe in Baltimore harbor with the containership Dali. It’s called “general average,” and it has to do with who pays when a ship runs into expensive trouble during a voyage.

This law can force those customers whose cargo is on the ship to help pay for the cost of the disaster. Mostly it ends up being a complex negotiation between many insurance companies, but it could be an expensive caveat for small businesses who may not have insured their cargo sufficiently.