In the course of the rise of the modern state system, diplomats became invested with various privileges and immunities, part and parcel of the convenient but necessary fiction that ambassadors and their entourage occupied within their country of posting (the "territorial" sovereign) an enclave of their own sovereign power. Thus persons and property of the "sending state" enjoyed within the protected zone customary (so-called extraterritorial) rights and were exempt from the normal reach of the executive and judicial power of the host or "receiving state," to cite the language of the two Vienna conventions of 1961 and 1963 governing diplomatic and consular practice, respectively. Accordingly, an embassy could by custom extend the protection of its premises to fugitives from the summary justice or even lynch law of the host country. (Warships and merchant vessels were treated similarly.)
This tradition of diplomatic asylum became particularly strong in Latin America during the nineteenth century—a reflection of the political violence that frequently accompanied regime changes within the continent. By custom such asylum was not extended to ordinary criminals ("persons accused of or condemned for common crimes") but rather to "political offenders," those refugees whose only offense, it was asserted, lay in their beliefs. To regulate this tradition, in the first half of the twentieth century the Latin American republics negotiated a series of conventions (Havana in 1928, Montevideo in 1933, Caracas in 1954), though not all the countries ratified the results. The Caracas convention followed a bitterly fought dispute between Peru and Colombia before the International Court of Justice at The Hague. In two connected decisions, the Asylum and Haya de la Torre cases, 1950–1951, the court held that the right of diplomatic asylum did not exist through customary international law but, if at all, only by virtue of explicit bilateral or multilateral treaties, or through the established and reciprocal action of both countries. (Ironically, in the absence of a legal solution, the court urged the parties to resolve their dispute by negotiations and compromise, in other words, through what in lay terms would be called diplomacy.) Surveying the history and jurisprudence of diplomatic asylum, sub voce the scholar and advocate Ian Brownlie writes that, despite the examples drawn from "Latin American regional custom, … it is very doubtful if a right of asylum for either political or other offenders is recognized by general international law."
The United States, like other major powers, has generally disapproved of the invocation of diplomatic immunity for fugitives. But not long after the eventual resolution of the Colombian-Peruvian case, the U.S. embassy in Budapest granted diplomatic asylum to the Roman Catholic primate of Hungary, Joseph Cardinal Mindszenty, as the Americans registered their profound opposition to the Soviet repression of the Hungarian uprising in October–November 1956. This episode—an exception to normal U.S. policy—was a deliberate Cold War tactic and has to be seen as part of a larger pattern of American diplomatic and legal responses to the political and ideological challenges of communism. At the end of the Korean War (1950–1953), for example, the U.S.–led United Nations negotiators offered asylum en masse to North Korean and mainland Chinese prisoners of war who did not wish to be repatriated to their home countries.