Are there any rules governing relics?

I recommend either holding on to the relics for veneration or giving them away.

One thing that you cannot do with the relics is sell them. The Code of Canon Law strictly prohibits the sale of relics: “It is absolutely forbidden to sell sacred relics” (CIC 1190 §1). This law pertains to all authentic relics of saints. The New Commentary on the Code of Canon Law explains that, “The prohibition against selling any sacred relic is expressed in the code’s strongest language, nefas est, meaning ‘it is absolutely forbidden.’ Relics may be given away by their owners, except for the second category of relics which may not be given away without permission of the Apostolic See” (1415).

The second category of relics referred to in the commentary are very significant or highly honored relics. The law treats these relics more strictly: “Relics of great significance and other relics honored with great reverence by the people cannot be alienated validly in any manner or transferred permanently without the permission of the Apostolic See” (CIC 1190 §2). The commentary explains relics of great significance: “A significant relic was defined in the previous code as a part of a saint’s body (arm, forearm, heart, tongue, leg) or the part of a martyr’s body that had suffered the wound that caused death, provided the part was entire and not too small” (1415).