It looks like criminality by theft and fraud.
TREASURE TROVE. Found treasure.
2. This name is given to such money or coin, gold, silver, plate, or bullion, which having been hidden or concealed in the earth or other private place, so long that its owner is unknown, has been discovered by accident. Should the owner be found it must be restored to him; and in case of not finding him, the property, according to the English law, belongs to the king. In the latter case, by the civil law, when the treasure was found by the owner of the soil, he was considered as entitled to it by the double title of owner and finder; when found on another’s property, one-half belonged to the owner of the estate, and the other to the finder; when found on public property, it belonged one-half to the public treasury, and the other to the finder. Lecons du Dr. Rom. Sec. 350-352. This includes not only gold and silver, but whatever may constitute riches, as vases, urns, statues, &c.
3. The Roman definition includes the same things under the word pecunia; but the thing found must have a commercial value for ancient tombs would not be considered a treasure. The thing must have been hidden or concealed in the earth; and no one must be able to establish his right to it. It must be found, by a pure accident, and not in consequence of search. Dall. Dict. Propriete, art. 3, s. 3.
4. According to the French law, le tresor est toute chose cachee ou enfouie, sur laquelle personne ne peut justifier sa propriete, et qui est decouverte par lo pur effet du hasard. Code Civ. 716. Vide 4 Toull. n. 34. Vide, generally, 20 Vin. Abr. 414; 7 Com. Dig. 649; 1 Bro. Civ. Law, 237; 1 Blackstone’s Comm. 295; Poth. Traite du Dr. de Propreite, art. 4.
A Law Dictionary, Adapted to the Constitution and Laws of the United States. By John Bouvier. Published 1856.