Are inventions in all fields patentable?

While the patent system is created to safeguard inventions, not all inventions are eligible for patent protection due to reasons such as operability, public order, or industrial policy. Each country can draw up a list of excluded objects and/or subject matters. However, the public interest is not always consistent among countries and may change over time. For instance, France may allow patents for gambling devices, whereas China and Japan do not. It is also important to note that obtaining a patent does not necessarily mean that the patented product can be freely distributed in the market. For example, although new models of military equipment or drugs can be protected by patents, they may not be allowed to enter the market without proper approval or testing.