as sacred and religious buildings and gifts solemnly dedicated to the service of  God, as chalices, crosses and censers, which it is forbidden to alienate except to  ransom captives. Cemeteries are also sacred places,24 as are churches and chapels,  and though the buildings are destroyed their sites still remain sacred.25 A sacred  thing differs from a sacrarium, for that is the place where sacred things are kept.  There are also things subject to a sanction,26 as the walls and gates of cities, which  are called such because capital punishment is decreed for those who commit any  outrage upon them,27 violating them either by admitting persons through them or  scaling them by ladders or in any other way, for it is a hostile and disgraceful act  to enter in any way except by the gates. That is said to be subject to a sanction which  is protected and fortified against the wrongs of men, and that law especially called  a sanction which imposes a penalty on a wrongdoer. No person is permitted to  rebuild the city walls for his private advantage, only for the public welfare.28
Some things belong to no one.
 29Things are said to be res nullius in several different ways: by nature or the  jus naturale, as wild beasts, birds and fish; by the common opinion of mankind,30  as was said [above], as things sacred, religious or subject to a sanction; by accident,  as an inheritance lying vacant before it is taken up. But the rule fails in this case  because the inheritance represents the persona of the deceased31 or because [the  advent] of a future heir who will take it up is expected.32 Things taken as derelict  are likewise said to be res nullius.33 They are also said to become such through lapse  of time, as treasure trove. 34 Also where there is no apparent owner of the thing,  as in wreck, and the same is true of things regarded as waif, as cattle, where there  is no apparent owner, all of which formerly belonged to the finder by natural law  but are now made the property of the prince by the jus gentium.3536There are  things that are res nullius by nature, which nature does not permit to be anyone's  property, as free men.37 Free men are not subjects of ownership and commerce and  the same may be said of a sick slave his lord has cast off. The law declares him to  be free.38