Natural and legal rights are two types of rights. Natural rights are those that are not dependent on the laws or customs of any particular culture or government, and therefore universal and inalienable (i.e., rights that cannot be repealed or restrained by human laws). Legal rights are those bestowed onto a person by a given legal system (i.e., rights that can be modified, repealed, and restrained by human laws).
The concept of natural law is related to the concept of natural rights. Natural law first appeared in ancient Greek philosophy, and was referred to by Roman philosopher Cicero. It was subsequently alluded to in the Bible, and was then developed in the Middle Ages by Catholic philosophers such as Albert the Great and his pupil Thomas Aquinas. During the Age of Enlightenment, the concept of natural laws was used to challenge the divine right of kings, and became an alternative justification for the establishment of a social contract, positive law, and government – and thus legal rights – in the form of classical republicanism. Conversely, the concept of natural rights is used by others to challenge the legitimacy of all such establishments.
The idea of human rights is also closely related to that of natural rights: some acknowledge no difference between the two, regarding them as synonymous, while others choose to keep the terms separate to eliminate association with some features traditionally associated with natural rights. Natural rights, in particular, are considered beyond the authority of any government or international body to dismiss. The 1948 United Nations Universal Declaration of Human Rights is an important legal instrument enshrining one conception of natural rights into international soft law. Natural rights were traditionally viewed as exclusively negative rights, whereas human rights also comprise positive rights. Even on a natural rights conception of human rights, the two terms may not be synonymous.