Isopoliteia

An isopoliteia (Ancient Greek: ἰσοπολιτεία) was a treaty of equal citizenship rights between the poleis (city-states) of ancient Greece. This happened through either mutual agreement between cities or through exchange of individual decrees. It was used to cement amicable diplomatic relations. The Aetolian League was a unique case of a larger political entity which granted isopoliteia treaties. Sympoliteia goes further, merging the governments of two or more poleis.