Inviolability of person is a cornerstone of diplomatic law, codified in Article 29 of the Vienna Convention on Diplomatic Relations (VCDR, 1961), which states that a diplomatic agent shall not be liable to any form of arrest or detention and that the receiving state shall treat the diplomat with due respect and take all appropriate steps to prevent any attack on their person, freedom, or dignity.
The rule is absolute in the sense that it admits no exception for the gravity of the alleged offense: even a diplomat suspected of a serious crime cannot be detained, though the receiving state may declare them persona non grata under Article 9 and require their departure. Inviolability is distinct from, though related to, immunity from jurisdiction (Articles 31–32): inviolability protects the physical person from coercive measures, while immunity bars adjudication. A diplomat may be briefly restrained only in exceptional circumstances such as self-defense or to prevent an imminent serious crime, a narrow customary exception acknowledged in state practice.
The principle extends through related instruments: Article 40 of the Vienna Convention on Consular Relations (1963) affords a lesser, qualified inviolability to consular officers, and the 1973 Convention on the Prevention and Punishment of Crimes against Internationally Protected Persons criminalizes attacks on diplomats and certain officials.
Receiving states bear a positive obligation to protect diplomats, not merely to refrain from coercion themselves. Failures of this duty have generated international responsibility, most notably in the United States Diplomatic and Consular Staff in Tehran (US v. Iran) case before the ICJ in 1980, where Iran was held responsible for failing to protect US diplomatic personnel during the 1979 embassy seizure.
Inviolability ends when the diplomat's functions terminate and they have had a reasonable period to leave the country, though immunity for acts performed in an official capacity persists.
Example
When the United Kingdom considered entering the Ecuadorian embassy in London to arrest Julian Assange in 2012, it ultimately refrained, in part because doing so would have implicated the inviolability of accredited personnel and premises under the Vienna Convention.