Suzerainty (/ˈsuːzərənti, -rɛnti/) is a relationship in which one state or other polity controls the foreign policy and relations of a tributary state, while allowing the tributary state to have internal autonomy.[1] The dominant state is called the “suzerain”.
Suzerainty differs from sovereignty in that the tributary state is technically independent, but enjoys only limited self-rule. Although the situation has existed in a number of historical empires, it is considered difficult to reconcile with 20th- or 21st-century concepts of international law, in which sovereignty is a binary which either exists or does not. While a sovereign state can agree by treaty to become a protectorate of a stronger power, modern international law does not recognise any way of making this relationship compulsory on the weaker power. Suzerainty is a practical, de facto situation, rather than a legal, de jure one.