A free market can only operate when some basic conditions have been met. One of these is the condition that exchange of private property is possible. It’s important to realize that private property is both a normative concept but also a legal reality: in everyday life, private property exists because there are contracts and title deeds that prove that something is my private property.  This legal dimension of private property is key to realizing how the government can make free markets work even for common and public goods. The key is to create private property rights that are rivalrous and excludable, and enforce them accordingly. It is these private property rights that are traded, not necessarily the good itself (The Private Production of Public Goods, 1970).  For the public good of roads, the private property right the government can create is the right to operate a toll booth on that road. For the common good of fisheries, the government can create conditional exploitation rights to private actors, and for carbon dioxide emitting industries, the government can create limited, tradable emissions rights. The most well-known example of government created private property rights is intellectual property: even though listening to music is non-rivalrous and with the internet, relatively non-excludable, the government’s enforcement of intellectual property allows a business like iTunes to survive and thrive.