The excerpt discusses the fundamental maritime laws established in the nineteenth century that govern the conduct of war at sea. Specifically, these rules, known as cruiser rules or prize law, dictate that a warship can intercept and search a merchant vessel but must protect its crew and ensure the ship is taken to port for legal evaluation by a prize court. These regulations have been respected by all naval forces throughout history and aim to maintain a level of humanity even during warfare.

Importantly, the rules explicitly prohibit attacks on passenger ships, emphasizing the protection of civilian lives during conflicts. The context provided is relevant to the events surrounding the sinking of the Lusitania, a merchant ship targeted during World War I. The narrative draws attention to the ethical considerations of maritime warfare and reinforces the idea that the adherence to these codes is crucial for maintaining order and safety in international waters.