Although it is a concept which has existed in a number of historical empires, it is a concept that is very difficult to describe using 20th- or 21st-century theories of international law, in which sovereignty either exists or does not. While a sovereign nation can agree by treaty to become a protectorate of a stronger power, modern international law does not recognize any way of making this relationship compulsory on the weaker power.
The word is often spelled "suzerainity", though this has come to be considered incorrect.
This system broke down in the 18th and 19th centuries in two ways. First during the 17th century, China was ruled by the ethnically Manchu Qing dynasty which ruled a multi-ethnic empire and justified their rule through different theories of rulership. While not contradicting traditional Han Chinese theories of the emperor as universal rule, the Qing did begin to make a distinction between areas of the world which they ruled and areas which they did not. The system also broke down as China faced European powers whose theories of sovereignty were based on international law and relations between equal states.
One way European states attempted to describe the relations between the Qing Dynasty and its outlying regions was in terms of suzerainty, although this did not at all match the traditional Chinese diplomatic theory.
India no longer looks after the external, defence, communications, and foreign affairs of Bhutan. However India provides substantial support to the Royal Bhutan Army and guarantees its support against external aggression. This is one of several situations in international politics where two sovereign states agree to have the more powerful administer the defense of the weaker.
Located in the Arabian Sea, Lakshadweep is a Union Territory of India off the coast of the south western state of Kerala. The Amindivi group of islands (Amini, Kadmat, Kiltan, Chetlat and Bitra) came under the rule of Tipu Sultan in 1787. They passed on to British control after the Third Anglo-Mysore War and were attached to the South Canara district. The rest of the islands became a suzerainty of the Arakkal family of Cannanore in return for a payment of annual tribute. After a while, the British took over the administration of those islands for non-payment of arrears. These islands were attached to the Malabar district of the Madras Presidency. In 1956, the States Reorganisation Act separated these islands from the mainland administrative units, forming a new union territory by combining all the islands.
After the First Boer War (1880–81), the South African Republic was granted its independence, albeit under British suzerainty. During the Second Boer War (1899–1902), the South African Republic was annexed as the Colony of the Transvaal, which existed until 1910, when it became the Province of Transvaal in the Union of South Africa.
Despite being occupied by the Axis powers, several Western and Asian countries were allowed to exercise self-rule. Several states were created in order to facilitate their occupation, including Vichy France, Manchukuo, the Empire of Vietnam, the Independent State of Croatia in Croatia and the Lokot Autonomy in Central Russia.
In modern geopolitics, it is common for larger countries to look after the defense and foreign relations of nearby smaller countries. Usually, this differs from traditional suzerainty in that the lesser party retains the right to abrogate the arrangement following a referendum. Some prominent examples include: