In light of recent international developments, such as the People’s Republic of China’s declaration of an air defense identification zone (ADIZ) in the East China Sea and the intercepts of military aircraft in international airspace adjacent to the nations of Europe, this article seeks to advance legal discussion and provide an updated perspective on the applicable international law of the sea and airspace, air defense measures, and the freedom of navigation. First, it examines the inherent differences between national airspace and international airspace. Second, it discusses the air defense measure known as ADIZ. Third, it discusses the air defense measure known as aircraft intercepts. Fourth, it discusses the freedom of navigation, and discusses ways in which the air defense measures of ADIZs and aircraft intercepts can be employed in a manner consistent with the freedom of navigation. By highlighting applicable U.S. laws, regulations, policy directives, and press releases, this article seeks to provide an example of effectively balancing security and freedom in a manner that is fully consistent with international law. In the end, this article concludes that air defense measures established and implemented by a nation may be lawful under international law, but only if the nation follows a “rules-based approach,” in which it conforms those measures to the applicable body of international law and respects the freedom of navigation enjoyed by other nations.