In domestic law, the central question that this book seeks to answer – how strongly should international law be protected and enforced? – was addressed in the early 1970s in a seminal Harvard Law Review article by Guido Calabresi and Douglas Melamed. Much like Hohfeld sixty years before them, Calabresi and Melamed warned against indiscriminate use of the term legal “right.” Yet, whereas Hohfeld distinguished between rights (corresponding to a duty), privileges, powers and immunities, Calabresi and Melamed referred to a broad pool of legal “entitlements.” In their view, all of law can be seen as rules for the ownership and exchange (forcible or voluntary) of entitlements. They used the term “entitlements” instead of “rights” as the very purpose of their analysis was to discern different types of legal rights based on the degree of legal protection that they enjoy. As the common usage of the term “right” often corresponds to just one type of entitlement (namely those protected by a so-called property rule), the broader term of entitlements was needed to avoid confusion and to encapsulate not just one but all types of entitlements.

Calabresi and Melamed provided a three-step scale of protection for domestic legal entitlements. In their view, a first group of entitlements is best protected as “inalienable,” that is, not to be changed or transferred at all, not even if the entitlement's holder agrees.