The idea of a province was that of an aggregate of states (_civitates_); where Greek or Phoenician civilisation had penetrated, these states were cities, but sometimes, as in Gaul and Spain, they were cantons or tribes. Natural political associations were usually chosen as the units of government, although formidable combinations were broken up, and the numerical regulation of the government centres in a province was an integral part of its organisation. Thus the number of communal unions was in Sicily 68,[1488] in Asia 44,[1489] and 64 in Transalpine Gaul.[1490] Such aggregates probably include the free and federate states, which, although geographically, were not juristically within the province at all. The cities which were _liberae_ and those which were _liberae et foederatae_ differed, sometimes perhaps in the degree, but always in the basis, of their rights. The latter had the grant of their rights embodied in a sworn treaty (_foedus_), which was the product in the earlier Republic of Senate and people, in the later of either of these powers,[1491]—a guarantee which was meant to be perpetual, and the breach of which was either an act of war or its result. A charter (_lex data_), on the other hand,[1492] which made a city only “free” might be revoked at any moment. The rights common to both groups of states are practically those of the Italian communes[1493]—a control of their own finances, a free enjoyment of their land which exempted them from the payment of tribute, and above all a use and enjoyment of their own native law[1494]—and both agree in being entirely outside the sphere of the governor’s jurisdiction.[1495] He could enter such a privileged city only as a guest, and although for purposes of convenience great central cities which were free, as Antioch in Syria and Thessalonica in Macedonia, were, from their position as natural capitals, chosen as the residence of the governor, he merely exercised jurisdiction in these towns, not over their citizens. More distant still from provincial rule were the allied kings (_reges socii_) on the frontiers. Their independence was less conditioned than that of the free and allied cities, for they were bound to furnish less definite assistance to Rome in time of need, and their foreign activity was not wholly destroyed. But the chief reason why in a list of Rome’s friends they appear in a separate category[1496] is that a treaty with a king was not, like one with a Republic, regarded as eternal. It was a personal obligation, and its perpetual validity depended on its renewal with each successive occupant of the throne.