Pressures on the archaeological resource, at both a national and an international level, have never been so great. Increasing population numbers, industrialisation, mechanised cultivation, expanding settlements and an international market for antiquities are causing immense destruction of archaeological sites and their contents. In reaction to this pressure, and the resultant losses, managers of the heritage resource have to make difficult decisions as to the selection and preservation of individual sites at international, national and even local levels. Many of these decisions are guided by national and international legislation such as Britain's Ancient Monuments and Archaeological Areas Act of 1979, its Planning (Listed Buildings and Conservation Areas) Act 1990 and UNESCO's 1972 Convention Concerning the Protection of the World Cultural and Natural Heritage. Despite some voiced misgivings concerning issues of criteria and value (Darvill 1995; Pressoyre 1996; Schaafsma 1989), most managers rely heavily on these instruments. This chapter will investigate the conceptual underpinnings of such legislation.