inter se (in-t<<schwa>>r seeorsay). [Latin “between or among themselves”] (Of a right or duty) owed between the parties rather than to others. — Also termed inter sese (in-t<<schwa>>r see-see).

“[T]he law of nations is, or at least includes, a branch of natural law, namely, the rules of natural justice as applicable to the relations of states inter se.” John Salmond, Jurisprudence 32 (Glanville L. Williams ed., 10th ed. 1947).

[Blacks Law 8th]