What type of good becomes a public good when it is non-rivalrous after a legal ruling regarding ownership?

The correct answer identifies a public good due to its non-rivalrous nature following a legal ruling about ownership. Public goods are characterized by two main properties: they are non-excludable and non-rivalrous. The term "non-rivalrous" means that one person's use of the good does not reduce its availability to others. When a legal ruling changes the ownership of a good, making it accessible to all without restriction, it becomes non-excludable and can be enjoyed by anyone without diminishing its availability.

This transition illustrates how certain goods can shift to being classified as public goods under specific conditions—particularly when legal frameworks alter access. In contrast, the other options typically retain characteristics that do not afford them the public good status. Club goods, for example, are excludable but non-rivalrous; private goods are both excludable and rivalrous; and common goods are rivalrous and non-excludable, which differs fundamentally from the defining traits of public goods. Thus, understanding how legal rulings impact the nature of goods can highlight their classification within economic theory.