Mare igitur proprium omnino alicuius fieri non potest, quia natura commune hoc esse non permittit, sed iubet, immo ne litus quidem;[73a] nisi quod haec addenda est interpretatio; ut si quid earum rerum per naturam occupari possit, id eatenus occupantis fiat, quatenus ea occupatione usus ille promiscuus non laeditur. Quod merito receptum est; nam cum ita se habet, cessat utraque exceptio per quam evenisse diximus, ne omnia in eius proprium transcriberentur.
Quoniam igitur inaedificatio species est occupationis, in litore licet aedificare, si id fieri potest sine ceterorum incommodo,[74a] ut Pomponius loquitur, quod ex Scaevola explicabimus, nisi usus publicus, hoc est communis impediretur. Et qui aedificaverit, soli dominus fiet, quia id solum nec ullius proprium, nec ad usum communem necessarium fuit. Est igitur occupantis; sed non diutius quam durat occupatio, quia reluctari mare possessioni videtur, exemplo ferae, quae si in naturalem se libertatem receperit, non ultra captoris est, ita et litus postliminio mari cedit.
Quicquid autem privatum fieri occupando, idem et publicum, hoc est populi proprium posse ostendimus.[75a] Sic litus Imperi Romani finibus inclusum, populi Romani esse Celsus
Therefore the sea can in no way become the private property of any one, because nature not only allows but enjoins its common use.[73] Neither can the shore become the private property of any one. The following qualification, however, must be made. If any part of these things is by nature susceptible of occupation, it may become the property of the one who occupies it only so far as such occupation does not affect its common use. This qualification is deservedly recognized. For in such a case both conditions vanish through which it might eventuate, as we have said, that all of it would pass into private ownership.
Since therefore, to cite Pomponius, building is one kind of occupation, it is permissible to build upon the shore, if this can be done without inconvenience to other people;[74] that is to say (I here follow Scaevola) if such building can be done without hindrance to public or common use of the shore. And whoever shall have constructed a building under the aforesaid circumstances will become the owner of the ground upon which said building is; because this ground is neither the property of any one else, nor is it necessary to common use. It becomes therefore the property of the occupier, but his ownership lasts no longer than his occupation lasts, inasmuch as the sea seems by nature to resist ownership. For just as a wild animal, if it shall have escaped and thus recovered its natural liberty, is no longer the property of its captor, so also the sea may recover its possession of the shore.
We have now shown that whatever by occupation can become private property can also become public property, that is, the private property of a whole nation.[75] And so Celsus considered the shore included within the limits of the Roman Empire to be the property of the Roman people.