The general principle of the measure was, therefore, the limitation to five hundred _jugera_ of the amount of public land that could be "possessed" by an individual. The very definition of the tenure immediately exempted large portions of the State's domain from the operation of this rule.[335] The Campanian land was leased by the State to individuals, not merely possessed by them as the result of an occupation permitted by the government; it, therefore, fell outside the scope of the measure;[336] but, as it was technically public land and its ownership was vested in the State, it would have been hazardous to presume its exemption; it seems, therefore, to have been specifically excluded from the operation of the bill, and a similar exception was probably made in favour of many other tracts of territory held under a similar tenure.[337] Either Gracchus declined to touch any interest that could properly describe itself as "vested," even though it took merely the form of a leasehold, or he valued the secure and abundant revenue which flowed into the coffers of the State from these domains. There were other lands strictly "public" where the claim of the holders was still stronger, and where dispossession without the fullest compensation must have been regarded as mere robbery. We know from later legislation that respect was had to such lands as the Trientabula, estates which had been granted by the Roman government at a quit rent to its creditors, as security for that portion of a national debt which had never been repaid. It is less certain what happened in the case of lands of which the usufruct alone had been granted to communities of Roman citizens or Latin colonists. Ownership in this case still remained vested in the Roman people, and if the right of usufruct had been granted by law, it could be removed by law. In the case of Latin communities, however, it was probably guaranteed by treaty, which no mere law could touch: and so similar were the conditions of Roman and Latin communities in this particular, that it is probable that the land whose use was conferred on whole communities by these ancient grants, was wholly spared by the Gracchan legislation. In the case of those commons which were possessed by groups of villagers for the purposes of pasturage (_ager compascuus_),[338] it is not likely that the group was regarded as the unit: and therefore, even in the case of such an aggregate possessing over five hundred _jugera_, their occupation was probably left undisturbed.