Back to Mom’s head. She could create a written, signed, dated document explicitly stating that she wants you to have her skull after she dies. It would be similar to the document people sign if they want to donate their body for scientific research. But even with that paperwork, and aforementioned head removal, my funeral home could not legally hand over the decapitated head, because of something called abuse-of-corpse laws. These laws vary from place to place, and can sometimes seem a little arbitrary. For example, the law in Kentucky says you’re committing corpse abuse if you treat a dead body in a way that “would outrage ordinary family sensibilities.” But what is an “ordinary family”? Maybe in your “ordinary family” Dad was a scientist who always promised that when he died, he would leave you both his collection of Bunsen burners and his skull.

Read: Your bones live on without you

Abuse-of-corpse laws exist for a reason. They protect people’s bodies from being mistreated (ahem, necrophilia). They also prevent a corpse from being snatched from the morgue and used for research or public exhibition without the dead person’s consent. History is littered with such violations. Medical professionals have stolen corpses and even dug up fresh graves to get bodies for dissection and research. Then there are cases like that of Julia Pastrana, a 19th-century Mexican woman with a condition called hypertrichosis, which caused hair to grow all over her face and body. After she died, her husband saw that there was money to be made by displaying Pastrana in freak shows, so he took her embalmed and taxidermied corpse on world tour. Pastrana had ceased to be regarded as human; her corpse had become a possession.

Because of abuse-of-corpse laws, nobody’s dead body can be claimed as property. “Finders keepers” doesn’t apply here. But unfortunately, those same laws prevent you from plopping Mom’s skull on your bookcase.

So where do skulls on bookcases come from? In the United States, no federal law prevents owning, buying, or selling human remains, unless the remains are Native American. Otherwise, whether you’re able to sell or own human remains is decided by each individual state. At least 38 states have laws that should prevent the sale of human remains, but in reality the laws are vague, confusing, and enforced at random. In one seven-month period in 2012–13, 454 human skulls were listed on eBay, with an average opening bid of just under $650 (eBay subsequently banned the practice).

Many skulls for private sale have questionable origins, sourced from the thriving bone trades in India and China. The bones are usually obtained from people who couldn’t afford cremation or burial. So to be clear: You can’t own your own mother’s corpse, but if you are willing to engage in some suspect internet commerce, a femur from the other side of the world might make its way into your home.