The burial of pet remains in cemeteries designated for humans is illegal in many U.S. states. Like other laws surrounding funerals, these are often based on a cultural sense of what is appropriate. The anthropologist Mary Thurston traces them back to the institutionalization of Christianity. With time, “animal practices were discouraged as it was accepted that humans were the only beings with souls,” she told CNN in 2010.

A debate over who is worthy of death rituals makes the concept of whole-family cemeteries controversial. In 2009, Washington state tried to pass legislation allowing for the burial of pets in human cemeteries, and an employee of the Washington Cemetery and Funeral Association laid out her argument against the bill:

Cemeteries in this state are formed for the purpose of the burial “of the human dead.” Try going back to the families who in good faith bought their graves in the knowledge that it was people-only. Try telling people of various religious faiths who believe various animals are anathema. Try telling your family member who is deathly afraid of dogs that, sorry, there's a good chance you're going to be buried next to a dog.

For others, being buried next to their dog is their final wish. When Greene first started the Green Pet-Burial Society, a surge of people found the group’s website through Google searches. “They would put in ‘human cemetery’ or ‘can I be buried with my dog,’” he explains. As they began writing to him, asking if there were such cemeteries near where they lived, Greene decided to set up a directory. It’s now by far the most visited page on the site.

Despite laws and policies, some pet lovers apparently are finding ways to make these burials happen. “There are just numerous stories of people sneaking the cremains of a beloved pet into the casket of somebody who has passed,” Greene says. “And the question is, why should people have to sneak around at a period of grief and bereavement?”

Greene wants laws that allow individual cemeteries to decide for themselves whether they want to offer the option of burying animals alongside their owners. But states have been taking a largely piecemeal approach to legalization. Last year, New York allowed the burial of animal remains in human cemeteries—with the caveat that both humans and pets must be interred at the same time. Other states are interested in whole-family cemeteries, but only to a point.

Greene has contacted more than 20 different legislators in his home state of California, and says many told him they would be willing to support legislation but wouldn’t introduce it. “This just wasn’t a priority,” he explains.

Whether or not it should be depends, in part, on what people consider to be the role of pets in their lives. “It was clear to me from the beginning that people consider their pets part of their family,” says Ellen Macdonald, the owner of Eloise Woods Community Natural Burial Park in Cedar Creek, Texas. “For some people, pets are their only family.”