Separate Opinion 10 G.R. No. 224469 for their communities under a claim of private ownership. Thus, these are indisputably presumed to have been held in this way before the Spanish Conquest. Expanding on this peculiar nature of ancestral domains, which he describes as neither public nor private land~, former Chief Justice Reynato S. Puno, in his Separate Opinion in Cruz v. Secretary of Environment and Natural Resources 26 ( Cruz), stated: The right of ownership and possession of the ICCs/lPs to their ancestral domains is held under the indigenous concept of ownership. This concept maintains the view that ancestral domains are the ICCs/Ips['] private but community property. It is private simply because it is not part of the public domain. But its private character ends there. The ancestral domain is owned in common by the ICCs/lPs and not by one particular person. The IPRA itself provides that areas within the ancestral domains, whether delineated or not, are presumed to be communally held. These communal rights, however, are not exactly the same as co-ownership rights under the Civil Code. Co-ownership gives any co-owner the right to demand partition of the property held in common. The Civil Code expressly provides that "[nJo co-owner shall be obliged to remain in the co-ownership." Each co-owner may demand at any time the partition of the thing in common, insofar as his share is concerned. To allow such a right over ancestral domains may be destructive not only of customary law of the community but ofthe,very~community itself. Communal rights over land are not the same as corporate rights over real property, much less corporate condominium rights. A corporation can exist only for a maximum of fifty (50) years subject to an extension of another fifty years in any single instance. Every stockholder has the right to disassociate himself from the corporation. Moreover, the corporation itself may be dissolved voluntarily or involuntarily. Communal rights to the land are held not only by the present possessors of the land but extends to all generations of the ICCs/IPs, past, present and future, to the domain. This is the reason why the ancestral domain must be kept within the ICCs/IPs themselves. The domain cannot be transferred, sold or conveyed to other persons. It belongs to the ICCs/IPs as a community. 27 Chief Justice Puno went on to state that "[fjollowing the constitutional mandate that 'customary law govern property rights or relations in determining the ownership and extent of q,ncestral domains,' the IPRA, by legislative fiat, introduces a new concept ofownership. This is a concept that has long existed under customary law." 28 He continues: Custom, from which customary law is derived, is also recognized under the Civil Code as a source of law. Some articles of the Civil Code expressly provide that custom should be applied in cases where no codal provision is applicable. In other words, in the absence of any 26 27 28 G.R. No. 135385, December 6, 2000, 347 SCRA 128. Id. at 222-223. (Emphasis and underscoring supplied, italics omitted) Id. at 223.