Whether the longstanding Cape Cod custom giving ownership of a bomb-lanced fin-back whale to the person who killed it was valid and enforceable.
Holding
Yes. The custom was reasonable and valid, so Ghen acquired title when he killed the whale.
Reasoning
The custom was settled, long accepted, and confined to a small and specialized industry. Every whaling crew used distinctive marks on its lances, allowing the whale's killer to be identified, and the custom had gone undisputed for many years. A trade-wide custom of this kind did not threaten the general law of property or disturb ordinary commercial expectations.
The rule required the first taker to do everything that was practically possible to appropriate this particular animal. A fin-back whale could not be taken by harpoon and line because of its speed, and a whale killed with a bomb-lance immediately sank. The killer therefore could not retain physical possession or mark it in a more direct way before it disappeared beneath the water.
The custom was necessary to preserve the fishery. Without a rule protecting the hunter who killed the whale, a chance finder could take the value of the hunter's labor and investment. That risk would deter people from undertaking the dangerous, skilled, and capital-intensive work of hunting these whales. The custom also protected finders by allowing reasonable salvage for reporting or securing the whale.
Prior whaling cases supported recognition of specialized customs where they reflected the practical realities of the trade. In particular, cases recognizing possession through anchoring a dead whale or through the industry rule that 'the iron holds the whale' showed that property rules may accommodate established whaling practices. The court also observed that ordinary common-law principles might reach the same result because Ghen had done all that the circumstances permitted to make the whale his own.