What term describes a power or demand established by law?

The term that best describes a power or demand established by law is "right." In the context of legal and social frameworks, a right is an entitlement that individuals have, which is recognized and protected by law. Rights can be considered guarantees that ensure individuals are afforded certain freedoms and protections under the legal system. This includes civil liberties, human rights, and various legal entitlements that influence how individuals interact with one another and with the government.

In contrast, privilege refers to a special advantage or benefit granted to a person or group, often based on certain characteristics and not universally established by law. Responsibility implies a duty or obligation that one has toward others or society, while obligation refers to something one is bound to do, often imposed by societal norms or legal requirements. While these other terms relate to duties, privileges, or societal roles, they do not convey the same legal entitlements that "rights" do.