This chapter examines instances in which an expansive concept of “self-defence” has been advanced by a state to justify using force to protect citizens abroad, either by military rescue or by forcibly deterring those who threaten their safety.

Powerful states have long claimed a legal right to use military force (“gun-boat diplomacy”) to this end. In the nineteenth-century case of Durand v. Hollins, the US Circuit Court of Appeals said:

At issue in Durand was the President's constitutional authority, without obtaining a Congressional declaration of war, to order a naval bombardment of San Juan del Norte (Greytown), Nicaragua, as reprisal against those of its inhabitants who “had perpetrated acts of violence against the US nationals and their property.” Although in upholding this exercise of plenary power, the Court was declaring US, not international, law, it acted in recognition of what it claimed was the widespread state practice of “humanitarian intervention” and “citizen rescue.”

These practices, whatever their currency at that earlier time, have now become problematic.