The legal rights of nonhuman animals might first be achieved in any of three ways. Most agree that the least likely will be through the re-interpretation or amendment of state or federal constitutions, or through international treaties. For example, the Treaty of Amsterdam that came into force on May 1, 1999, formally acknowledged that nonhuman animals are “sentient beings” and not merely goods or agricultural products. The European Community and the member states signatory to the treaty are required “to pay full regard to the welfare requirements of animals.” In 2002 the German Parliament amended Article 26 of the Basic Law to give nonhuman animals the right to be “respected as fellow creatures” and to be protected from “avoidable pain.” Half of the sixteen German states already have some sort of animal rights provisions in their constitutions.
In the United States, most believe that gaining personhood is much more probable through legislative enactment than through a constitutional change. But a change in the common law (which Germany does not have) may be the most likely of all. What is the common law? Lemuel Shaw, the nineteenth century chief justice of the Supreme Judicial Court of Massachusetts, provided this good definition: it “consists of a few broad and comprehensive principles, founded on reason, natural justice, and enlightened public policy, modified and adapted to all the circumstances of all the particular cases that fall within it.”
Why the common law over legislation? The common law is created by English-speaking judges while in the process of deciding cases. Unlike legislators, judges are at least formally bound to do justice. Properly interpreted, the common law is meant to be flexible, adaptable to changes in public morality, and sensitive to new scientific discoveries. Among its chief values are liberty and equality. These favor common law personhood, as a matter of liberty, at least for those nonhuman animals, such as chimpanzees, bonobos, gorillas, orangutans, dolphins, and whales, who possess such highly advanced cognitive abilities as consciousness, perhaps even self-consciousness; a sense of self; and the abilities to desire and act intentionally. In other words, they have what I call a “practical autonomy,” which is, I argue, sufficient, though not necessary, for basic legal rights. An animal’s species is irrelevant to his or her entitlement to liberty rights; any who possesses practical autonomy has what is sufficient for basic rights as a matter of liberty. And as long as society awards personhood to non-autonomous humans, such as the very young, the severely retarded, and the persistently vegetative, then it must also award basic rights, as a matter of equality as well, to nonhuman animals with practical autonomy.