Fetialis

This was the mode in which Roman treaties were made, the fecialis praying Jupiter to punish the infringer of the treaty as he did the animal, which he instantly dispatched with a flint stone.

[...] but when the theatre of war became more distant, the fetialis, consul, or praetor, contented himself with hurling his lance from a pillar near the temple of Bellona in the direction of the hostile territory, while the declaration of war itself was made by the military commander of the province through an ambassador.

Fetiales also investigated allies' claims of abuse by Romans; if substantiated, the fetiales delivered the men accused to the injured parties.