Post was hunting a fox on a beach on Long Island with his hounds and was in hot pursuit when Pierson, knowing that Post was chasing the fox, killed and captured it. Post sued Pierson for trespass, claiming that his pursuit of the fox gave him a property right in the animal. The fox was wild and unowned (ferae naturae) before the incident.
Does a person acquire property rights in a wild animal by pursuing it with the intent to capture it, or is actual capture required to establish ownership?
Property rights in wild animals (ferae naturae) are acquired only through actual capture or mortal wounding followed by continued pursuit. Mere pursuit, even with intent to capture, does not establish property rights. The rule of capture requires either physical possession or circumstances that make capture inevitable.
The court held that Post did not acquire property rights in the fox through mere pursuit. Pierson, who actually killed and captured the fox, acquired ownership. Post's pursuit alone was insufficient to establish a property claim.
The majority, citing ancient authorities like Justinian's Institutes and Pufendorf, reasoned that clear rules are necessary to prevent disputes over wild animals. Requiring actual capture provides certainty and prevents endless litigation over who was "closest" to capturing an animal. The court noted that allowing mere pursuit to establish ownership would create too much uncertainty and conflict.
This case established the fundamental rule of capture in property law and demonstrates how legal systems create clear rules for acquiring property rights in unowned resources. The principle extends beyond hunting to oil, gas, water, and other natural resources. It illustrates the tension between rewarding effort and providing legal certainty.
Pierson v. Post remains the classic introduction to property law, teaching fundamental concepts about how property rights are acquired and the importance of clear legal rules. The case demonstrates the balance between rewarding effort and providing legal certainty in property acquisition.