Section 51(xxxi) is a subclause of section 51 of the Constitution of Australia. It empowers the Commonwealth to make laws regarding the acquisition of property, but stipulates that such acquisitions must be on just terms. The terms is sometimes referred to in shorthand as the 'just terms' provision. Aside from its importance to Australian Constitutional Law, and Property Law; the section is notable for its role as a plot device in The Castle, an iconic Australian film.